Method and system to start and use combination filler wire feed and high intensity energy source for root pass welding of the inner diameter of clad pipe

ABSTRACT

A welding system includes at least one high intensity energy source to create a weld puddle during a root pass on a narrow joint of a workpiece with a clad layer. The system also includes a controller to control a weld ramp out process such that, as the molten puddle advances to a start of an existing root pass weld, the controller at least one of decreases an energy output of the at least one high intensity energy source and reduces an interaction time between the at least one high intensity energy source and the weld puddle. After completion of the root pass, a thickness of a root pass weld in a region that is at or near the start point of the existing root pass weld is in a range of 100 percent to 130 percent of a nominal root pass thickness of a remainder of the root pass weld.

INCORPORATION BY REFERENCE

The present application claims priority to Provisional Application61/949,422, filed Mar. 7, 2014, which is incorporated herein byreference in its entirety.

TECHNICAL FIELD

Certain embodiments relate to filler wire overlaying applications aswell as welding and joining applications. More particularly, certainembodiments relate to a system and method to start and use a combinationfiller wire feed and energy source system for any of brazing, cladding,building up, filling, hard-facing overlaying, joining and weldingapplications.

BACKGROUND

The traditional filler wire method of welding (e.g., a gas-tungsten arcwelding (GTAW) filler wire method) provides increased deposition ratesand welding speeds over that of traditional arc welding alone. Thefiller wire, which leads a torch, is resistance-heated by a separatepower supply. The wire is fed through a contact tube toward a workpieceand extends beyond the tube. The extension can be resistance-heated asit approaches the puddle. A tungsten electrode may be used to heat andmelt the workpiece to form the weld puddle. The power supply provides alarge portion of the energy needed to resistance-melt the filler wire.In some cases, the wire feed may slip or faulter and the current in thewire may cause an arc to occur between the tip of the wire and theworkpiece. The extra heat of such an arc may cause burnthrough, spatterand poor surface quality. The risk of such an arc occurring is greaterat the start of the process where the wire initially comes in contactwith the workpiece at a small point. If the initial current in the wireis too high, the point may burn away, causing an arc to occur. Further,known systems have significant difficulty in joining aluminum to steel.

Further limitations and disadvantages of conventional, traditional, andproposed approaches will become apparent to one of skill in the art,through comparison of such approaches with embodiments of the presentinvention as set forth in the remainder of the present application withreference to the drawings.

SUMMARY

Embodiments of the present invention comprise a system and method tostart and use a combination filler wire feeder and energy source system.A first embodiment of the present invention comprises a method to startand use a combination wire feed and energy source system for any ofbrazing, cladding, building up, filling, hard-facing overlaying, weldingand joining applications. The method includes applying a sensing voltagebetween at least one resistive filler wire and a workpiece via a powersource and advancing a distal end of the at least one resistive fillerwire toward the workpiece. The method further includes sensing when thedistal end of the at least one resistive filler wire first makes contactwith the workpiece. The method also includes turning off the powersource to the at least one resistive filler wire over a defined timeinterval in response to the sensing. The method further includes turningon the power source at an end of the defined time interval to apply aflow of heating current through at least one resistive filler wire. Themethod also includes applying energy from a high intensity energy sourceto the workpiece to heat the workpiece at least while applying the flowof heating current. The high intensity energy source may include atleast one of a laser device, a plasma arc welding (PAW) device, a gastungsten arc welding (GTAW) device, a gas metal arc welding (GMAW)device, a flux cored arc welding (FCAW) device, and a submerged arcwelding (SAW) device. Methods of the present invention are also used tojoin dissimilar materials, such as joining aluminum to steel.

In another exemplary embodiment, a welding system includes at least onehigh intensity energy source to create a weld puddle during a root passon a narrow joint of a workpiece with a clad layer. The system includesa wire feeder that advances a filler wire to the weld puddle. A fillerwire power source provides a filler wire heating signal to heat thefiller wire when the filler wire is in contact with the weld puddle. Thesystem also includes a controller to control a weld ramp out processsuch that, as the molten puddle advances to a start of an existing rootpass weld, the controller controls the at least one high intensityenergy source to at least one of decrease an energy output of the atleast one high intensity energy source and reduce an interaction timebetween the at least one high intensity energy source and the weldpuddle. The controller also controls the wire feeder to either reducewire feed speed or stop the advancement of the filler wire. Thecontroller further controls the filler wire power source to eitherreduce a power level of the filler wire heating signal or stop thefiller wire heating signal to the filler wire. In addition, the weldramp out process is controlled such that, after completion of the rootpass, a thickness of a root pass weld in a region that is at or near thestart point of the existing root pass weld is in a range of 100 percentto 130 percent of a nominal root pass thickness of a remainder of theroot pass weld.

In another exemplary embodiment, a welding method includes creating aweld puddle using at least one high intensity energy source and weldinga root pass on a narrow joint of a workpiece with a clad layer. Themethod also includes advancing a filler wire to the weld puddle andheating a filler wire when the filler wire is in contact with the weldpuddle. The method further includes controlling a weld ramp out process,as the molten puddle advances to a start of an existing root pass weld.The controlling of the weld ramp out process includes at least one ofdecreasing an energy output of the at least one high intensity energysource and reducing an interaction time between the at least one highintensity energy source and the weld puddle. The controlling alsoincludes either reducing a wire feed speed of the filler wire orstopping the advancement of the filler wire. The controlling furtherincludes either reducing a power level of the filler wire heating signalor stopping the heating of the filler wire. In addition, the weld rampout process is controlled such that, after completion of the root pass,a thickness of a root pass weld in a region that is at or near the startpoint of the existing root pass weld is in a range of 100 percent to 130percent of a nominal root pass thickness of a remainder of the root passweld.

These and other features of the claimed invention, as well as details ofillustrated embodiments thereof, will be more fully understood from thefollowing description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a functional schematic block diagram of an exemplaryembodiment of a combination filler wire feeder and energy source systemfor any of brazing, cladding, building up, filling, and hard-facingoverlaying applications;

FIG. 2 illustrates a flow chart of an embodiment of a start-up methodused by the system of FIG. 1;

FIG. 3 illustrates a flow chart of an embodiment of a post start-upmethod used by the system of FIG. 1;

FIG. 4 illustrates a first exemplary embodiment of a pair of voltage andcurrent waveforms associated with the post start-up method of FIG. 3;

FIG. 5 illustrates a second exemplary embodiment of a pair of voltageand current waveforms associated with the post start-up method of FIG.3;

FIGS. 6 and 6A illustrate a further exemplary embodiment of the presentinvention used to perform a welding operation;

FIGS. 7, 7A, and 7B illustrate additional exemplary embodiments ofwelding with the present invention;

FIG. 8 illustrates a further exemplary embodiment of joining two sidesof a joint at the same time;

FIG. 9 illustrates another exemplary embodiment of welding with thepresent invention;

FIG. 10A illustrates another exemplary embodiments of the presentinvention in welding a joint with multiple lasers and wires;

FIGS. 10B-10C illustrate an aluminum to steel weld joint in accordancewith exemplary embodiments of the present invention;

FIGS. 11A to 11C depict exemplary embodiments of contact tips used withembodiments of the present invention;

FIG. 12 illustrates a hot wire power supply system in accordance with anembodiment of the present invention;

FIGS. 13A-C illustrate voltage and current waveforms created byexemplary embodiments of the present invention;

FIG. 14 illustrates another welding system in accordance an exemplaryembodiment of the present invention;

FIG. 15 illustrates an exemplary embodiment of a weld puddle created byan embodiment of the present invention;

FIGS. 16A to 16F illustrate exemplary embodiments of weld puddles andlaser beam utilization in accordance with embodiments of the presentinvention;

FIG. 17 illustrates a welding system in accordance with anotherexemplary embodiment of the present invention;

FIG. 18 illustrates an exemplary embodiment of a ramp down circuit whichcan be used in embodiments of the present invention;

FIG. 19 illustrates an exemplary embodiment of a fume extraction nozzlein accordance with the present invention;

FIG. 20 illustrates an exemplary embodiment of a further welding systemof the present invention;

FIG. 21 illustrates an exemplary embodiment of a welding operation inaccordance with an embodiment of the present invention;

FIG. 22A-22C illustrate exemplary embodiments of current waveformsutilized by welding systems of the present invention;

FIG. 23 illustrates an exemplary embodiment of another welding operationin accordance with an embodiment of the present invention;

FIG. 24 illustrates an another exemplary embodiment of current waveformsthat can be used with embodiments of the present invention;

FIG. 25 illustrates an exemplary embodiment of another welding operationthat can be used with embodiments of the invention;

FIG. 25A illustrates an exemplary embodiment a current waveforms thatcan be used with the embodiment shown in FIG. 25;

FIG. 26 illustrates an exemplary embodiment of a further weldingoperation using side-by-side arc welding operations;

FIG. 27 illustrates an exemplary embodiment of an additional weldingoperation of the present invention;

FIG. 28 illustrates an additional exemplary embodiment of a weldingoperation of the present invention utilizing magnetic steering; and

FIGS. 29 to 31 illustrate the creation of a root pass in a workpiecehaving a clad layer with exemplary embodiments of the present invention;and

FIGS. 32 and 33 illustrate an exemplary completion of the root passshown in FIG. 31, using exemplary embodiments of the present invention.

DETAILED DESCRIPTION

The term “overlaying” is used herein in a broad manner and may refer toany applications including brazing, cladding, building up, filling, andhard-facing. For example, in a “brazing” application, a filler metal isdistributed between closely fitting surfaces of a joint via capillaryaction. Whereas, in a “braze welding” application the filler metal ismade to flow into a gap. As used herein, however, both techniques arebroadly referred to as overlaying applications.

FIG. 1 illustrates a functional schematic block diagram of an exemplaryembodiment of a combination filler wire feeder and energy source system100 for performing any of brazing, cladding, building up, filling,hard-facing overlaying, and joining/welding applications. The system 100includes a laser subsystem capable of focusing a laser beam 110 onto aworkpiece 115 to heat the workpiece 115. The laser subsystem is a highintensity energy source. The laser subsystem can be any type of highenergy laser source, including but not limited to carbon dioxide,Nd:YAG, Yb-disk, YB-fiber, fiber delivered or direct diode lasersystems. Further, even white light or quartz laser type systems can beused if they have sufficient energy. Other embodiments of the system mayinclude at least one of an electron beam, a plasma arc weldingsubsystem, a gas tungsten arc welding subsystem, a gas metal arc weldingsubsystem, a flux cored arc welding subsystem, and a submerged arcwelding subsystem serving as the high intensity energy source. Thefollowing specification will repeatedly refer to the laser system, beamand power supply, however, it should be understood that this referenceis exemplary as any high intensity energy source may be used. Forexample, a high intensity energy source can provide at least 500 W/cm².The laser subsystem includes a laser device 120 and a laser power supply130 operatively connected to each other. The laser power supply 130provides power to operate the laser device 120.

The system 100 also includes a hot filler wire feeder subsystem capableof providing at least one resistive filler wire 140 to make contact withthe workpiece 115 in the vicinity of the laser beam 110. Of course, itis understood that by reference to the workpiece 115 herein, the moltenpuddle is considered part of the workpiece 115, thus reference tocontact with the workpiece 115 includes contact with the puddle. The hotfiller wire feeder subsystem includes a filler wire feeder 150, acontact tube 160, and a hot wire power supply 170. During operation, thefiller wire 140, which leads the laser beam 110, is resistance-heated byelectrical current from the hot wire welding power supply 170 which isoperatively connected between the contact tube 160 and the workpiece115. In accordance with an embodiment of the present invention, the hotwire welding power supply 170 is a pulsed direct current (DC) powersupply, although alternating current (AC) or other types of powersupplies are possible as well. The wire 140 is fed from the filler wirefeeder 150 through the contact tube 160 toward the workpiece 115 andextends beyond the tube 160. The extension portion of the wire 140 isresistance-heated such that the extension portion approaches or reachesthe melting point before contacting a weld puddle on the workpiece. Thelaser beam 110 serves to melt some of the base metal of the workpiece115 to form a weld puddle and also to melt the wire 140 onto theworkpiece 115. The power supply 170 provides a large portion of theenergy needed to resistance-melt the filler wire 140. The feedersubsystem may be capable of simultaneously providing one or more wires,in accordance with certain other embodiments of the present invention.For example, a first wire may be used for hard-facing and/or providingcorrosion resistance to the workpiece, and a second wire may be used toadd structure to the workpiece.

The system 100 further includes a motion control subsystem capable ofmoving the laser beam 110 (energy source) and the resistive filler wire140 in a same direction 125 along the workpiece 115 (at least in arelative sense) such that the laser beam 110 and the resistive fillerwire 140 remain in a fixed relation to each other. According to variousembodiments, the relative motion between the workpiece 115 and thelaser/wire combination may be achieved by actually moving the workpiece115 or by moving the laser device 120 and the hot wire feeder subsystem.In FIG. 1, the motion control subsystem includes a motion controller 180operatively connected to a robot 190. The motion controller 180 controlsthe motion of the robot 190. The robot 190 is operatively connected(e.g., mechanically secured) to the workpiece 115 to move the workpiece115 in the direction 125 such that the laser beam 110 and the wire 140effectively travel along the workpiece 115. In accordance with analternative embodiment of the present invention, the laser device 110and the contact tube 160 may be integrated into a single head. The headmay be moved along the workpiece 115 via a motion control subsystemoperatively connected to the head.

In general, there are several methods that a high intensity energysource/hot wire may be moved relative to a workpiece. If the workpieceis round, for example, the high intensity energy source/hot wire may bestationary and the workpiece may be rotated under the high intensityenergy source/hot wire. Alternatively, a robot arm or linear tractor maymove parallel to the round workpiece and, as the workpiece is rotated,the high intensity energy source/hot wire may move continuously or indexonce per revolution to, for example, overlay the surface of the roundworkpiece. If the workpiece is flat or at least not round, the workpiecemay be moved under the high intensity energy source/hot wire as shown ifFIG. 1. However, a robot arm or linear tractor or even a beam-mountedcarriage may be used to move a high intensity energy source/hot wirehead relative to the workpiece.

The system 100 further includes a sensing and current control subsystem195 which is operatively connected to the workpiece 115 and the contacttube 160 (i.e., effectively connected to the output of the hot wirepower supply 170) and is capable of measuring a potential difference(i.e., a voltage V) between and a current (I) through the workpiece 115and the hot wire 140. The sensing and current control subsystem 195 mayfurther be capable of calculating a resistance value (R=V/I) and/or apower value (P=V*I) from the measured voltage and current. In general,when the hot wire 140 is in contact with the workpiece 115, thepotential difference between the hot wire 140 and the workpiece 115 iszero volts or very nearly zero volts. As a result, the sensing andcurrent control subsystem 195 is capable of sensing when the resistivefiller wire 140 is in contact with the workpiece 115 and is operativelyconnected to the hot wire power supply 170 to be further capable ofcontrolling the flow of current through the resistive filler wire 140 inresponse to the sensing, as is described in more detail later herein. Inaccordance with another embodiment of the present invention, the sensingand current controller 195 may be an integral part of the hot wire powersupply 170.

In accordance with an embodiment of the present invention, the motioncontroller 180 may further be operatively connected to the laser powersupply 130 and/or the sensing and current controller 195. In thismanner, the motion controller 180 and the laser power supply 130 maycommunicate with each other such that the laser power supply 130 knowswhen the workpiece 115 is moving and such that the motion controller 180knows if the laser device 120 is active. Similarly, in this manner, themotion controller 180 and the sensing and current controller 195 maycommunicate with each other such that the sensing and current controller195 knows when the workpiece 115 is moving and such that the motioncontroller 180 knows if the hot filler wire feeder subsystem is active.Such communications may be used to coordinate activities between thevarious subsystems of the system 100.

FIG. 2 illustrates a flow chart of an embodiment of a start-up method200 used by the system 100 of FIG. 1. In step 210, apply a sensingvoltage between at least one resistive filler wire 140 and a workpiece115 via a power source 170. The sensing voltage may be applied by thehot wire power supply 170 under the command of the sensing and currentcontroller 195. Furthermore, the applied sensing voltage does notprovide enough energy to significantly heat the wire 140, in accordancewith an embodiment of the present invention. In step 220, advance adistal end of the at least one resistive filler wire 140 toward theworkpiece 115. The advancing is performed by the wire feeder 150. Instep 230, sense when the distal end of the at least one resistive fillerwire 140 first makes contact with the workpiece 115. For example, thesensing and current controller 195 may command the hot wire power supply170 to provide a very low level of current (e.g., 3 to 5 amps) throughthe hot wire 140. Such sensing may be accomplished by the sensing andcurrent controller 195 measuring a potential difference of about zerovolts (e.g., 0.4V) between the filler wire 140 (e.g., via the contacttube 160) and the workpiece 115. When the distal end of the filler wire140 is shorted to the workpiece 115 (i.e., makes contact with theworkpiece), a significant voltage level (above zero volts) may not existbetween the filler wire 140 and the workpiece 115.

In step 240, turn off the power source 170 to the at least one resistivefiller wire 140 over a defined time interval (e.g., severalmilliseconds) in response to the sensing. The sensing and currentcontroller 195 may command the power source 170 to turn off. In step250, turn on the power source 170 at an end of the defined time intervalto apply a flow of heating current through the at least one resistivefiller wire 140. The sensing and current controller 195 may command thepower source 170 to turn on. In step 260, apply energy from a highintensity energy source 110 to the workpiece 115 to heat the workpiece115 at least while applying the flow of heating current.

As an option, the method 200 may include stopping the advancing of thewire 140 in response to the sensing, restarting the advancing (i.e.,re-advancing) of the wire 140 at the end of the defined time interval,and verifying that the distal end of the filler wire 140 is still incontact with the workpiece 115 before applying the flow of heatingcurrent. The sensing and current controller 195 may command the wirefeeder 150 to stop feeding and command the system 100 to wait (e.g.,several milliseconds). In such an embodiment, the sensing and currentcontroller 195 is operatively connected to the wire feeder 150 in orderto command the wire feeder 150 to start and stop. The sensing andcurrent controller 195 may command the hot wire power supply 170 toapply the heating current to heat the wire 140 and to again feed thewire 140 toward the workpiece 115.

Once the start up method is completed, the system 100 may enter a poststart-up mode of operation where the laser beam 110 and hot wire 140 aremoved in relation to the workpiece 115 to perform one of a brazingapplication, a cladding application, a build-up application, ahard-facing application, or a welding/joining operation. FIG. 3illustrates a flow chart of an embodiment of a post start-up method 300used by the system 100 of FIG. 1. In step 310, move a high intensityenergy source (e.g., laser device 120) and at least one resistive fillerwire 140 along a workpiece 115 such that the distal end of the at leastone resistive filler wire 140 leads or coincides with the high intensityenergy source (e.g., laser device 120) such that energy (e.g., laserbeam 110) from the high intensity energy source (e.g., laser device 120)and/or the heated workpiece 115 (i.e., the workpiece 115 is heated bythe laser beam 110) melts the distal end of the filler wire 140 onto theworkpiece 115 as the at least one resistive filler wire 140 is fedtoward the workpiece 115. The motion controller 180 commands the robot190 to move the workpiece 115 in relation to the laser beam 110 and thehot wire 140. The laser power supply 130 provides the power to operatethe laser device 120 to form the laser beam 110. The hot wire powersupply 170 provides electric current to the hot wire 140 as commanded bythe sensing and current controller 195.

In step 320, sense whenever the distal end of the at least one resistivefiller wire 140 is about to lose contact with the workpiece 115 (i.e.,provide a premonition capability). Such sensing may be accomplished by apremonition circuit within the sensing and current controller 195measuring a rate of change of one of a potential difference between(dv/dt), a current through (di/dt), a resistance between (dr/dt), or apower through (dp/dt) the filler wire 140 and the workpiece 115. Whenthe rate of change exceeds a predefined value, the sensing and currentcontroller 195 formally predicts that loss of contact is about to occur.Such premonition circuits are well known in the art for arc welding.

When the distal end of the wire 140 becomes highly molten due toheating, the distal end may begin to pinch off from the wire 140 ontothe workpiece 115. For example, at that time, the potential differenceor voltage increases because the cross section of the distal end of thewire decreases rapidly as it is pinching off. Therefore, by measuringsuch a rate of change, the system 100 may anticipate when the distal endis about to pinch off and lose contact with the workpiece 115. Also, ifcontact is fully lost, a potential difference (i.e., a voltage level)which is significantly greater than zero volts may be measured by thesensing and current controller 195. This potential difference couldcause an arc to form (which is undesirable) between the new distal endof the wire 140 and the workpiece 115 if the action in step 330 is nottaken. Of course, in other embodiments the wire 140 may not show anyappreciable pinching but will rather flow into the puddle in acontinuous fashion while maintaining a nearly constant cross-sectioninto the puddle.

In step 330, turn off (or at least greatly reduce, for example, by 95%)the flow of heating current through the at least one resistive fillerwire 140 in response to sensing that the distal end of the at least oneresistive filler wire 140 is about to lose contact with the workpiece115. When the sensing and current controller 195 determines that contactis about to be lost, the controller 195 commands the hot wire powersupply 170 to shut off (or at least greatly reduce) the current suppliedto the hot wire 140. In this way, the formation of an unwanted arc isavoided, preventing any undesired effects such as splatter orburnthrough from occurring.

In step 340, sense whenever the distal end of the at least one resistivefiller wire 140 again makes contact with the workpiece 115 due to thewire 140 continuing to advance toward the workpiece 115. Such sensingmay be accomplished by the sensing and current controller 195 measuringa potential difference of about zero volts between the filler wire 140(e.g., via the contact tube 160) and the workpiece 115. When the distalend of the filler wire 140 is shorted to the workpiece 115 (i.e., makescontact with the workpiece), a significant voltage level above zerovolts may not exist between the filler wire 140 and the workpiece 115.The phrase “again makes contact” is used herein to refer to thesituation where the wire 140 advances toward the workpiece 115 and themeasured voltage between the wire 140 (e.g., via the contact tube 160)and the workpiece 115 is about zero volts, whether or not the distal endof the wire 140 actually fully pinches off from the workpiece 115 ornot. In step 350, re-apply the flow of heating current through the atleast one resistive filler wire in response to sensing that the distalend of the at least one resistive filler wire again makes contact withthe workpiece. The sensing and current controller 195 may command thehot wire power supply 170 to re-apply the heating current to continue toheat the wire 140. This process may continue for the duration of theoverlaying application.

For example, FIG. 4 illustrates a first exemplary embodiment of a pairof voltage and current waveforms 410 and 420, respectively, associatedwith the post start-up method 300 of FIG. 3. The voltage waveform 410 ismeasured by the sensing and current controller 195 between the contacttube 160 and the workpiece 115. The current waveform 420 is measured bythe sensing and current controller 195 through the wire 140 andworkpiece 115.

Whenever the distal end of the resistive filler wire 140 is about tolose contact with the workpiece 115, the rate of change of the voltagewaveform 410 (i.e., dv/dt) will exceed a predetermined threshold value,indicating that pinch off is about to occur (see the slope at point 411of the waveform 410). As alternatives, a rate of change of currentthrough (di/dt), a rate of change of resistance between (dr/dt), or arate of change of power through (dp/dt) the filler wire 140 and theworkpiece 115 may instead be used to indicate that pinch off is about tooccur. Such rate of change premonition techniques are well known in theart. At that point in time, the sensing and current controller 195 willcommand the hot wire power supply 170 to turn off (or at least greatlyreduce) the flow of current through the wire 140.

When the sensing and current controller 195 senses that the distal endof the filler wire 140 again makes good contact with the workpiece 115after some time interval 430 (e.g., the voltage level drops back toabout zero volts at point 412), the sensing and current controller 195commands the hot wire power supply 170 to ramp up the flow of current(see ramp 425) through the resistive filler wire 140 toward apredetermined output current level 450. In accordance with an embodimentof the present invention, the ramping up starts from a set point value440. This process repeats as the energy source 120 and wire 140 moverelative to the workpiece 115 and as the wire 140 advances towards theworkpiece 115 due to the wire feeder 150. In this manner, contactbetween the distal end of the wire 140 and the workpiece 115 is largelymaintained and an arc is prevented from forming between the distal endof the wire 140 and the workpiece 115. Ramping of the heating currenthelps to prevent inadvertently interpreting a rate of change of voltageas a pinch off condition or an arcing condition when no such conditionexists. Any large change of current may cause a faulty voltage readingto be taken due to the inductance in the heating circuit. When thecurrent is ramped up gradually, the effect of inductance is reduced.

FIG. 5 illustrates a second exemplary embodiment of a pair of voltageand current waveforms 510 and 520, respectively, associated with thepost start-up method of FIG. 3. The voltage waveform 510 is measured bythe sensing and current controller 195 between the contact tube 160 andthe workpiece 115. The current waveform 520 is measured by the sensingand current controller 195 through the wire 140 and workpiece 115.

Whenever the distal end of the resistive filler wire 140 is about tolose contact with the workpiece 115, the rate of change of the voltagewaveform 510 (i.e., dv/dt) will exceed a predetermined threshold value,indicating that pinch off is about to occur (see the slope at point 511of the waveform 510). As alternatives, a rate of change of currentthrough (di/dt), a rate of change of resistance between (dr/dt), or arate of change of power through (dp/dt) the filler wire 140 and theworkpiece 115 may instead be used to indicate that pinch off is about tooccur. Such rate of change premonition techniques are well known in theart. At that point in time, the sensing and current controller 195 willcommand the hot wire power supply 170 to turn off (or at least greatlyreduce) the flow of current through the wire 140.

When the sensing and current controller 195 senses that the distal endof the filler wire 140 again makes good contact with the workpiece 115after some time interval 530 (e.g., the voltage level drops back toabout zero volts at point 512), the sensing and current controller 195commands the hot wire power supply 170 to apply the flow of heatingcurrent (see heating current level 525) through the resistive fillerwire 140. This process repeats as the energy source 120 and wire 140move relative to the workpiece 115 and as the wire 140 advances towardsthe workpiece 115 due to the wire feeder 150. In this manner, contactbetween the distal end of the wire 140 and the workpiece 115 is largelymaintained and an arc is prevented from forming between the distal endof the wire 140 and the workpiece 115. Since the heating current is notbeing gradually ramped in this case, certain voltage readings may beignored as being inadvertent or faulty due to the inductance in theheating circuit.

In summary, a method and system to start and use a combination wire feedand energy source system for any of brazing, cladding, building up,filling, and hard-facing overlaying applications are disclosed. Highintensity energy is applied onto a workpiece to heat the workpiece. Oneor more resistive filler wires are fed toward the workpiece at or justin front of the applied high intensity energy. Sensing of when a distalend of the one or more resistive filler wires makes contact with theworkpiece at or near the applied high intensity energy is accomplished.Electric heating current to the one or more resistive filler wires iscontrolled based on whether or not the distal end of the one or moreresistive filler wires is in contact with the workpiece. The appliedhigh intensity energy and the one or more resistive filler wires aremoved in a same direction along the workpiece in a fixed relation toeach other.

In further exemplary embodiments, systems and methods of the presentinvention are employed for welding or joining operations. Theembodiments discussed above have focused on the use of filler metals inoverlaying operations. However, aspects of the present invention can beused in welding and joining applications in which workpieces are joinedusing welding operations and the use of a filler metal. Althoughdirected to overlaying a filler metal, the above described embodiments,systems and methods are similar to that employed in welding operations,described more fully below. Therefore, in the following discussions itis understood that the discussions above generally apply, unlessotherwise stated. Further, the following discussion may includereference to FIGS. 1 through 5.

It is known that welding/joining operations typically join multipleworkpieces together in a welding operation where a filler metal iscombined with at least some of the workpiece metal to form a joint.Because of the desire to increase production throughput in weldingoperations, there is a constant need for faster welding operations,which do not result in welds which have a substandard quality.Furthermore, there is a need to provide systems which can weld quicklyunder adverse environmental conditions, such as in remote work sites. Asdescribed below, exemplary embodiments of the present invention providesignificant advantages over existing welding technologies. Suchadvantages include, but are not limited to, reduced total heat inputresulting in low distortion of the workpiece, very high welding travelspeeds, very low spatter rates, welding with the absence of shielding,welding plated or coated materials at high speeds with little or nospatter and welding complex materials at high speeds.

In exemplary embodiments of the present invention, very high weldingspeeds, as compared to arc welding, can be obtained using coatedworkpieces, which typically require significant prep work and are muchslower welding processes using arc welding methods. As an example, thefollowing discussion will focus on welding galvanized workpieces.Galvanization of metal is used in increase the corrosion resistance ofthe metal and is desirable in many industrial applications. However,conventional welding of galvanized workpieces can be problematic.Specifically, during welding the zinc in the galvanization vaporizes andthis zinc vapor can become trapped in the weld puddle as the puddlesolidifies, causing porosity. This porosity adversely affects thestrength of the weld joint. Because of this, existing welding techniquesrequire a first step of removing the galvanization or welding throughthe galvanization at lower processing speeds and with some level ofdefects—which is inefficient and causes delay, or requires the weldingprocess to proceed slowly. By slowing the process the weld puddleremains molten for a longer period of time allowing the vaporized zincto escape. However, because of the slow speed production rates are slowand the overall heat input into the weld can be high. Other coatingswhich can cause similar issues include, but are not limited to: paint,stamping lubricants, glass linings, aluminized coatings, surface heattreatment, nitriding or carbonizing treatments, cladding treatments, orother vaporizing coatings or materials. Exemplary embodiments of thepresent invention eliminate these issues, as explained below.

Turning to FIGS. 6 and 6A (cross-section and side view, respectively) arepresentative welding lap joint is shown. In this figure two coated(e.g., galvanized) workpieces W1/W2 are to be joined with a lap weld.The lap joint surfaces 601 and 603 are initially covered with thecoating as well as the surface 605 of workpiece W1. In a typical weldingoperation (for example GMAW) portions of the covered surface 605 aremade molten. This is because of the typical depth of penetration of astandard welding operation. Because the surface 605 is melted thecoating on the surface 605 is vaporized, but because of the distance ofthe surface 605 from the surface of the weld pool is large, the gasescan be trapped as the weld pool solidifies. With embodiments of thepresent invention this does not occur.

As shown in FIGS. 6 and 6A a laser beam 110 is directed from the laserdevice 120 to the weld joint, specifically the surfaces 601 and 603. Thelaser beam 110 is of an energy density to melt portions of the weldsurfaces creating molten puddles 601A and 603A, which creates a generalweld puddle. Further, a filler wire 140—which is resistance heated asdescribed previously—is directed to the weld puddle to provide theneeded filler material for the weld bead. Unlike most welding processesthe filler wire 140 makes contact and is plunged into the weld puddleduring the welding process. This is because this process does not use awelding arc to transfer the filler wire 140 but rather simply melts thefiller wire into the weld puddle.

Because the filler wire 140 is preheated to at or near its melting pointits presence in the weld puddle will not appreciably cool or solidifythe puddle and is quickly consumed into the weld puddle. The generaloperation and control of the filler wire 140 is as described previouslywith respect to the overlaying embodiments.

Because the laser beam 110 can be precisely focused and directed to thesurfaces 601/603, the depth of penetration for the pools 601A/603A canbe precisely controlled. By controlling this depth carefully,embodiments of the present invention prevent any unnecessary penetrationor melting of the surface 605. Because of the surface 605 is not overlymelted any coating on the surface 605 is not vaporized and does notbecome trapped in the weld puddle. Further, any coating on the surfaceof the weld joint 601 and 603 are easily vaporized by the laser beam 110and that gas is allowed to escape the weld zone before the weld puddlesolidifies. It is contemplated that a gas extraction system can beutilized to aid in the removal of any vaporized coating materials.

Because the depth of weld puddle penetration can be precisely controlledthe speed of welding coated workpieces can be greatly increased, whilesignificantly minimizing or eliminating porosity. Some arc weldingsystem can achieve good travel speeds for welding, but at the higherspeeds problems can occur such as porosity and spatter. In exemplaryembodiments of the present invention, very high travel speeds can beachieved with little or no porosity or spatter (as discussed herein) andin fact travel speeds of over 50 inches/min can be easily achieved formany different types of welding operations. Embodiments of the presentinvention can achieve welding travel speeds over 80 inches/minute.Further, other embodiments can achieve travel speeds in the range of 100to 150 inches/min with minimal or no porosity or spatter, as discussedherein. Of course, the speeds achieved will be a function of theworkpiece properties (thickness and composition) and the wire properties(e.g., dia.), but these speeds are readily achievable in many differentwelding and joining applications when using embodiments of the presentinvention. Further, these speeds can be achieved with either a 100%carbon dioxide shielding gas, or can be achieved with no shielding atall. Additionally, these travel speeds can be achieved without removingany surface coating prior to the creation of the weld puddle andwelding. Of course, it is contemplated that higher travel speeds can beachieved. Furthermore, because of the reduced heat input into the weldthese high speeds can be achieved in thinner workpieces 115, whichtypically have a slower weld speed because heat input must be kept lowto avoid distortion. Not only can embodiments of the present inventionachieve the above described high travel speeds with little or noporosity or spatter, but they can also achieve very high depositionrates, with low admixture. Specifically, embodiments of the presentinvention can achieve deposition rates of 10 lb/hr or higher with noshielding gas and little or no porosity or spatter. In some embodimentsthe deposition rate is in the range of 10 to 20 lb/hr.

In the exemplary embodiments of the present invention, these extremelyhigh travel speeds are achieved with little or no porosity and little orno spatter. Porosity of a weld can be determined by examining across-section and/or a length of the weld bead to identify porosityratios. The cross-section porosity ratio is the total area of porosityin a given cross-section over the total cross-sectional area of the weldjoint at that point. The length porosity ratio is the total accumulatedlength of pores in a given unit length of weld joint. Embodiments of thepresent invention can achieve the above described travel speeds with across-sectional porosity between 0 and 20%. Thus, a weld bead with nobubbles or cavities will have a 0% porosity. In other exemplaryembodiments, the cross-sectional porosity can be in the range of 0 to10%, and in another exemplary embodiment can be in the range of 2 to 5%.It is understood that in some welding applications some level ofporosity is acceptable. Further, in exemplary embodiments of theinvention the length porosity of the weld is in the range of 0 to 20%,and can be 0 to 10%. In further exemplary embodiments the lengthporosity ratio is in the range of 1 to 5%. Thus, for example, welds canbe produced that have a cross-sectional porosity in the range of 2 to 5%and a length porosity ratio of 1 to 5%.

Furthermore, embodiments of the present invention can weld at the aboveidentified travel speeds with little or no spatter. Spatter occurs whendroplets of the weld puddle are caused to spatter outside of the weldzone. When weld spatter occurs it can compromise the quality of the weldand can cause production delays as it must be typically cleaned off ofthe workpieces after the welding process. Thus, there is great benefitto welding at high speed with no spatter. Embodiments of the presentinvention are capable of welding at the above high travel speeds with aspatter factor in the range of 0 to 0.5, where the spatter factor is theweight of the spatter over a given travel distance X (in mg) over theweight of the consumed filler wire 140 over the same distance X (in Kg).That is:Spatter Factor=(spatter weight (mg)/consumed filler wire weight (Kg))

The distance X should be a distance allowing for a representativesampling of the weld joint. That is, if the distance X is too short,e.g., 0.5 inch, it may not be representative of the weld. Thus, a weldjoint with a spatter factor of 0 would have no spatter for the consumedfiller wire over the distance X, and a weld with a spatter of factor of2.5 had 5 mg of spatter for 2 Kg of consumed filler wire. In anexemplary embodiment of the present invention, the spatter factor is inthe range of 0 to 1. In a further exemplary embodiment, the spatterfactor is in the range of 0 to 0.5. In another exemplary embodiment ofthe present invention the spatter factor is in the range of 0 to 0.3. Itshould be noted that embodiments of the present invention can achievethe above described spatter factor ranges with or without the use of anyexternal shielding—which includes either shielding gas or fluxshielding. Furthermore, the above spatter factor ranges can be achievedwhen welding uncoated or coated workpieces, including workpieces whichare galvanized—without having the galvanization removed prior to thewelding operation.

There are a number of methods to measure spatter for a weld joint. Onemethod can include the use of a “spatter boat.” For such a method arepresentative weld sample is placed in a container with a sufficientsize to capture all, or almost all, of the spatter generated by a weldbead. The container or portions of the container—such as the top—canmove with the weld process to ensure that the spatter is captured.Typically the boat is made from copper so the spatter does not stick tothe surfaces. The representative weld is performed above the bottom ofthe container such that any spatter created during the weld will fallinto the container. During the weld the amount of consumed filler wireis monitored. After the weld is completed the spatter boat is to beweighed by a device having sufficient accuracy to determine thedifference, if any, between the pre-weld and post-weld weight of thecontainer. This difference represents the weight of the spatter and isthen divided by the amount, in Kg, of the consumed filler wire.Alternatively, if the spatter does not stick to the boat the spatter canbe removed and weighed by itself.

As described previously, the use of the laser device 120 allows forprecise control of the depth of the weld puddle. Furthermore, the use ofthe laser 120 permits easy adjustment of the size and depth of the weldpuddle. This is because the laser beam 110 can be focused/de-focusedeasily or have its beam intensity changed very easily. Because of theseabilities the heat distribution on the workpieces W1 and W2 can beprecisely controlled. This control allows for the creation of verynarrow weld puddles for precise welding as well as minimizing the sizeof the weld zone on the workpiece. This also provides advantages inminimizing the areas of the workpiece that are not affected by the weldbead. Specifically, the areas of the workpieces adjacent to the weldbead will have minimal affects from the welding operation, which isoften not the case in arc welding operations.

In exemplary embodiments of the present invention, the shape and/orintensity of the beam 110 can be adjusted/changed during the weldingprocess. For example, it may be necessary at certain places on aworkpiece to change the depth of penetration or to change the size ofthe weld bead. In such embodiments the shape, intensity, and/or size ofthe beam 110 can be adjusted during the welding process to provide theneeded change in the welding parameters.

As described above, the filler wire 140 impacts the same weld puddle asthe laser beam 110. In an exemplary embodiment, the filler wire 140impacts the weld puddle at the same location as the laser beam 110.However, in other exemplary embodiments the filler wire 140 can impactthe same weld puddle remotely from the laser beam. In the embodimentshown in FIG. 6A the filler wire 140 trails the beam 110 during thewelding operation. However, that is not necessary as the filler wire 140can be positioned in the leading position. The present invention is notlimited in this regard, as the filler wire 140 can be positioned atother positions relative to the beam 110 so long as the filler wire 140impacts the same weld puddle as the beam 110.

The above described embodiment was described with respect to workpieceswhich have a coating, such as galvanization. However, embodiments of thepresent invention can also be used on workpieces that have no coating.Specifically, the same above described welding process can be utilizedwith non-coated workpieces. Such embodiments achieve the sameperformance attributes as described above regarding coated metals.

Further, exemplary embodiments of the present invention are not limitedto welding steel workpieces, but can also be used for welding aluminum,or more complex metals—as will be described further below.

Another beneficial aspect of the present invention is related toshielding gas. In a typical arc welding operation a shielding gas orshielding flux is used to prevent the oxygen and nitrogen in theatmosphere, or other harmful elements, from interacting with the weldpuddle and metal transfer. Such interference can be detrimental to thequality and appearance of the weld. Therefore, in almost all arc weldingprocesses shielding is provided by the use of externally suppliedshielding gas, shielding gas created by the consumption of an electrodehaving flux on it (e.g., stick electrode, flux cored electrode, etc.) orby an externally supplied granulated flux (e.g., sub-arc welding).Further, in some welding operations, such as welding specialized metalsor welding galvanized workpieces, a special shielding gas mixture mustbe employed. Such mixtures can be extremely expensive. Further, whenwelding in extreme environments it is often difficult to transport largequantities of shielding gas to the work site (such as at pipelines), orwind tends to blow the shielding gas away from the arc. Further, the useof fume extraction systems has grown in recent years. While thesesystems tend to remove fumes they also tend to draw away shielding gasif placed to close to the welding operation.

Benefits of the present invention include being able to use minimalamounts or no shielding gas when welding. Alternatively, embodiments ofthe present invention allow the use of shielding gasses that wouldnormally not be able to be used for a specific welding operation. Thisis discussed further below.

When welding typical workpieces (non-coated) with an arc weldingprocess, shielding—regardless of its form—is required. It has beendiscovered that when welding with embodiments of the present invention,no shielding is required. That is no shielding gas, no granular flux andno self-shielding electrodes need be used. However, unlike in an arcwelding process, the present invention produces a quality weld. That is,the above described weld speeds can be achieved without the use of anyshielding. This could not have been accomplished with prior arc weldingprocesses.

During a typical arc welding process a molten droplet of the filler wireis transferred from the filler wire to the weld puddle through thewelding arc. Without shielding the entire surface of the droplet isexposed to the atmosphere during transfer and as such tends to pick upthe nitrogen and oxygen in the atmosphere and deliver the nitrogen andoxygen to the weld puddle. This is not desirable.

Because the present invention delivers the filler wire to the weldwithout the use of droplets, or similar processes, the filler wire isnot exposed to the atmosphere as much. Therefore, in many weldingapplications the use of shielding is not required. As such, not only canembodiments of the present invention achieve high welding speeds withlittle or no porosity or spatter, they can do so without the use ofshielding gas.

Without having to use shielding, it is possible to locate a fumeextraction nozzle much closer to the weld joint during welding, thusproviding more efficient and effective fume extraction. When a shieldinggas is employed it is necessary to place the fume extraction nozzle at alocation such that it does not interfere with the function of theshielding gas. Because of the advantages of the present invention, nosuch restriction exists and fume extraction can be optimized. Forexample, in an exemplary embodiment of the present invention the laserbeam 110 is protected by a laser shroud assembly 1901 which shields thebeam from the laser 120 to near the surface of the workpiece 115. Arepresentation of this can be seen in FIG. 19. The shroud 1901 (shown incross-section) protects the beam 110 from interference and providesadditional safety during operation. Furthermore, the shroud can becoupled to a fume extraction system 1903 which draws any welding fumesaway from the welding zone. Because embodiments can be utilized with noshielding gas the shroud 1901 can positioned very close to the weld todirectly draw the fumes away from the welding zone. In fact the shroud1901 can be positioned such that its distance Z above the weld is in therange of 0.125 to 0.5 inches. Of course, other distances can be used butcare must be taken not to disturb the weld puddle or to significantlydiminish the effectiveness of the shroud 1901. Because fume extractionsystems 1903 are generally understood and known in the welding industrytheir construction and operation will not be discussed in detail herein.Although FIG. 19 shows the shroud 1901 only protecting the beam 110, itis of course possible that the shroud 1901 be constructed such that itencompasses at least a portion of the wire 140 and contact tip 160. Forexample, it is possible that the bottom opening of the shroud 1901 belarge enough to cover nearly the entire weld puddle, or even be largerthan the weld puddle, to increase fume extraction.

In exemplary embodiments of the present invention used to weld coatedworkpieces, such as galvanized workpieces, a much less expensiveshielding gas may be employed. For example, a 100% CO₂ shielding gas canbe used for welding many different materials, including mild steels.This is also true when welding more complex metals, such as stainlesssteel, duplex steel and super duplex steel, which can be welded withonly a 100% nitrogen shielding gas. In typical arc welding operations,the welding of stainless steel, duplex steel or super-duplex steelrequires more complex mixtures of shielding gas, which can be quiteexpensive. Embodiments of the present invention allow these steels to bewelded with only a 100% nitrogen shielding gas. Further, otherembodiments can have these steels welded with no shielding. In a typicalwelding process for galvanized materials, a special mix shielding gasmust be utilized, such as an argon/CO₂ blend. This type of gas needs tobe used, in part, because during normal arc welding a cathode and anodeis present in the weld zone. However, as explained above and furtherexplained below, there is no welding arc and, as such, there is no anodeor cathode present in the weld zone. Therefore, the opportunity for thefiller metal to pick up harmful elements from the atmosphere is greatlyreduced, as there is no arc and no droplet transfer. It should be notedthat even though many embodiments of the present invention permitwelding without the use of shielding—like shielding gas—a gas flow canbe utilized over the weld to remove vapor or contaminates from the weldzone. That is, during welding it is contemplated that air, nitrogen,CO₂, or other gases, can be blown over the weld so as to removecontaminates from the weld zone.

In addition to be able to weld coated materials at high speeds,embodiments of the present invention can also be utilized to welddual-phase steels with a significantly reduced heat affected zone(“HAZ”). A dual-phase steel is a high strength steel having both aferrite and martensitic microstructure, thus allowing the steel to havehigh strength and good formability. Because of the nature of dual-phasesteels the strength of a dual phase steel weld is limited by thestrength of the heat affected zone. The heat affected zone is the zonearound the weld joint (not including the filler metal) which issignificantly heated from the welding process such that itsmicrostructure is adversely changed because of the arc welding process.In known arc welding processes the heat affected zone is quite largebecause of the size of the arc plasma and the high heat input into theweld zone. Because the heat affected zone is quite large the heataffected zone becomes the strength limiting portion of the weld. Assuch, arc welding processes typically use mild steel filler wires 140 toweld such joints (for example, ER70S-6, or -3 type electrodes) since theuse of high strength electrodes is unnecessary. Furthermore, because ofthis designers must locate welding joints in dual-phase steelsstrategically out of high stress structures—such as in automobileframes, bumpers, engine cradles, etc.

As discussed above the use of the laser device 120 provides high levelsof precision in the creation of the weld puddle. Because of thisprecision the heat affected zone surrounding the weld bead can be keptvery small, or the overall effect of the heat affected zone to theworkpiece can be minimized. In fact, in some embodiments the heataffected zone of the work piece can be nearly eliminated. This is doneby maintaining the focus of the laser beam 110 only on the portions ofthe workpiece in which a puddle is to be created. By significantlyreducing the size of the heat affected zone the strength of the basemetal is not compromised as much as if an arc welding process is used.As such, the presence or location of the heat affected zone is no longerthe limiting factor in the design of a welded structure. Embodiments ofthe present invention allow for the use of higher strength filler wiresbecause the composition and strength of the workpiece and the strengthof the filler wire can be the driving factors in a structural design,rather than the heat affected zone. For example, embodiments of thepresent invention now permit the use of electrodes having at least an 80ksi yield strength, such as ER80S-D2, type electrodes. Of course, thiselectrode is intended to be exemplary. Furthermore, because there isless overall heat input then from arc welding the cooling rates of thepuddle will be quicker, which means that the chemistry of the fillerwires used can be leaner but give equal or greater performance overexisting wire.

Additionally, exemplary embodiments of the present invention can be usedto weld titanium with significantly reduced shielding requirements. Itis known that when welding titanium with an arc welding process greatcare must be taken to ensure an acceptable weld is created. This isbecause during the welding process titanium has a strong affinity toreact with oxygen. The reaction between titanium and oxygen createstitanium dioxide, which if present in the weld pool may significantlyreduce the strength and/or ductility of the weld joint. Because of this,when arc welding titanium it is necessary to provide a significantamount of trailing shielding gas to shield not only the arc but thetrailing molten puddle from the atmosphere as the puddle cools. Becauseof the heat generated from arc welding the weld puddle can be quitelarge and remain molten for long periods of time, thus requiring asignificant amount of shielding gas. Embodiments of the presentinvention significantly reduce the time the material is molten andrapidly cools so the need for this extra shielding gas is reduced.

As explained above, the laser beam 110 can be focused very carefully tosignificantly reduce the overall heat input into the weld zone and thussignificantly reduce the size of the weld puddle. Because the weldpuddle is smaller the weld puddle cools much quicker. As such, there isno need for a trailing shielding gas, but only shielding at the weld.Further, for the similar reasons discussed above the spatter factor whenwelding titanium is greatly reduced while the rate of welding isincreased.

Turning now to FIGS. 7 and 7A, an open root type welding joint is shown.Open root joints are often used to weld thick plates and pipes and canoften occur in remote and environmentally difficult locations. There area number of known methods to weld open root joints, including shieldedmetal arc welding (SMAW), gas tungsten arc welding (GTAW), gas metal arcwelding (GMAW), flux cored arc welding (FCAW), submerged arc welding(SAW), and flux cored arc welding, self shielded (FCAW-S). These weldingprocesses have various disadvantages including the need for shielding,speed limitations, the creation of slag, etc.

Thus, embodiments of the present invention greatly improve theefficiencies and speeds at which these types of welds can be performed.Specifically, the use of shielding gas can be eliminated, or greatlyreduced, and the generation of slag can be completely eliminated.Furthermore, welding at high speeds can be obtained with minimal spatterand porosity.

FIGS. 7 and 7A show representative open root welding joints being weldedby exemplary embodiments of the present invention. Of course,embodiments of the present invention can be utilized to weld a widevariety of weld joints, not just lap or open root type joints. In FIG. 7a gap 705 is shown between the workpieces W1/W2 and each respectiveworkpiece has an angled surface 701/703, respectively. Just as discussedabove, embodiments of the present invention use a laser device 120 tocreate a precise molten puddle on the surfaces 701/703 and a pre-heatedfiller wire (not shown) is deposited into the puddles, respectively, asdescribed above.

In fact, exemplary embodiments of the present invention are not limitedto directing a single filler wire to each respective weld puddle.Because no welding arc is generated in the welding process describedherein, more than one filler wire can be directed to any one weldpuddle. By increasing the number of filler wires to a given weld puddlethe overall deposition rate of the weld process can be significantlyincreased without a significant increase in heat input. Thus, it iscontemplated that open root weld joints (such as the type shown in FIGS.7 and 7A) can be filled in a single weld pass.

Further, as shown in FIG. 7, in some exemplary embodiments of thepresent invention multiple laser beams 110 and 110A can be utilized tomelt more than one location in the weld joint at the same time. This canbe accomplished in a number of ways. In a first embodiment, shown inFIG. 7, a beam splitter 121 is utilized and coupled to the laser device120. A beam splitter 121 is known to those knowledgeable of laserdevices and need not be discussed in detail herein. The beam splitter121 splits the beam from the laser device 120 into two (or more)separate beams 110/110A and can direct them to two different surfaces.In such an embodiment multiple surfaces can be irradiated at the sametime, providing further precision and accuracy in welding. In anotherembodiment, each of the separate beams 110 and 110A can be created by aseparate laser device, such that each beam is emitted from its owndedicated device.

In such an embodiment, using multiple laser devices, many aspects of thewelding operation can be varied to adapt to different welding needs. Forexample, the beams generated by the separate laser devices can havedifferent energy densities; can have different shapes, and/or differentcross-sectional areas at the weld joint. With this flexibility, aspectsof the welding process can be modified and customized to fulfill anyspecific weld parameters needed. Of course, this can also beaccomplished with the utilization of a single laser device and a beamsplitter 121, but some of the flexibility may be limited with the use ofthe single laser source. Further, the present invention is not limitedto either a single or double laser configuration, as it is contemplatedthat any number of lasers can be used as desired.

In further exemplary embodiments, a beam scanning device can be used.Such devices are known in the laser or beam emitting arts and are usedto scan the beam 110 in a pattern over a surface of the workpiece. Withsuch devices the scan rates and patterns, as well as the dwell time, canbe used to heat the workpiece 115 in the desired fashion. Further, theoutput power of the energy source (e.g., laser) can be regulated asdesired to create the desired puddle formation. Additionally, the opticsemployed within the laser 120 can be optimized based on the desiredoperation and joint parameters. For example, line and integrator opticscan be utilized to produce a focused line beam for a wide welding orcladding operation or an integrator can be used to produce asquare/rectangular beam having a uniform power distribution.

FIG. 7A depicts another embodiment of the present invention, where asingle beam 110 is directed to the open root joint to melt the surfaces701/703.

Because of the precision of the laser beams 110 and 110A, the beams110/110A can be focused only on the surfaces 701/703 and away from thegap 705. Because of this, the melt-through (which would normally fallthrough the gap 705) can be controlled which greatly improves thecontrol of the back-side weld bead (the weld bead at the bottom surfaceof the gap 705).

In each of FIGS. 7 and 7A a gap 705 exists between the workpieces W1 andW2 which is filled with a weld bead 707. In an exemplary embodiment,this weld bead 705 is created by a laser device (not shown). Thus, forexample, during a welding operation a first laser device (not shown)directs a first laser beam (not shown) to the gap 705 to weld theworkpieces W1 and W2 together with the laser weld bead 707, while thesecond laser device 120 directs at least one laser beam 110/110A to thesurfaces 701/703 to create weld puddles where a filler wires(s) (notshown) is deposited to complete the weld. The gap weld bead 707 can becreated just by a laser, if the gap is small enough, or can be createdby the use of a laser and a filler wire if the gap 705 so requires.Specifically, it may be necessary to add filler metal to properly fillthe gap 705 and thus a filler wire should be used. The creation of thisgap bead 705 is similar to that described above with regard to variousexemplary embodiments of the present invention.

It should be noted that the high intensity energy sources, such as thelaser devices 120 discussed herein, should be of a type havingsufficient power to provide the necessary energy density for the desiredwelding operation. That is, the laser device 120 should have a powersufficient to create and maintain a stable weld puddle throughout thewelding process, and also reach the desired weld penetration. Forexample, for some applications lasers should have the ability to“keyhole” the workpieces being welded. This means that the laser shouldhave sufficient power to fully penetrate the workpiece, whilemaintaining that level of penetration as the laser travels along theworkpiece. Exemplary lasers should have power capabilities in the rangeof 1 to 20 kW, and may have a power capability in the range of 5 to 20kW. Higher power lasers can be utilized, but can become very costly. Ofcourse, it is noted that the use of the beam splitter 121 or multiplelasers can be used in other types of weld joints as well, and can beused in lap joints such as those shown in FIGS. 6 and 6A.

FIG. 7B depicts another exemplary embodiment of the present invention.In this embodiment a narrow groove, deep open root joint is shown. Whenarc welding deep joints (greater than 1 inch in depth) it can bedifficult to weld the bottom of the joint when the gap G for the grooveis narrow. This is because it is difficult to effectively delivershielding gas into such a deep groove and the narrow walls of the groovecan cause interference with the stability of a welding arc. Because theworkpiece is typically a ferrous material the walls of the joint caninterfere, magnetically, with the welding arc. Because of this, whenusing typical arc welding procedures the gap G of the groove needs to besufficiently wide so that the arc remains stable. However, the wider thegroove the more filler metal is needed to complete the weld. Becauseembodiments of the present invention do not require a shielding gas anddo not use a welding arc these issues are minimized. This allowsembodiments of the present invention to weld deep, narrow groovesefficiently and effectively. For example, in an exemplary embodiment ofthe present invention where the workpiece 115 has a thickness greaterthan 1 inch, the gap width G is in the range of 1.5 to 2 times thediameter of the filler wire 140 and the sidewall angle is in the rangeof 0.5 to 10 degrees. In an exemplary embodiment, the root passpreparation of such a weld joint can have a gap RG in the range of 1 to3 mm with a land in the range of 1/16 to ¼ inch. Thus, deep open rootjoints can be welded faster and with much less filler material thennormal arc welding processes. Further, because aspects of the presentinvention introduce much less heat into the welding zone, the tip 160can be designed to facilitate much closer delivery to the weld puddle toavoid contact with the side wall. That is, the tip 160 can be madesmaller and constructed as an insulated guide with a narrow structure.In a further exemplary embodiment, a translation device or mechanism canbe used to move the laser and wire across the width of the weld to weldboth sides of the joint at the same time.

As shown in FIG. 8 a butt-type joint can be welded with embodiments ofthe present invention. In FIG. 8 a flush butt-type joint is shown,however it is contemplated that butt-type joints with v-notch groves onthe upper and bottom surfaces of the weld joint can be also welded. Inthe embodiment shown in FIG. 8, two laser devices 120 and 120A are shownon either side of the weld joint, each respectively creating their ownweld puddle 801 and 803. Like FIGS. 7 and 7A the heated filler wires arenot shown as they are trailing behind the laser beams 110/110A in theview shown.

When welding butt-type joints with known arc technology there can besignificant problems with “arc blow”, which occurs when the magneticfields generated by welding arcs interfere with each other such that thearcs cause each other to move erratically. Further, when two or more arcwelding systems are being used to weld on a the same weld joint therecan be significant issues caused by the interference of the respectivewelding currents. Additionally, because of the depth of penetration ofarc welding methods, due to—in part—the high heat input, the thicknessesof the workpieces that can be welded with arcs on either side of theweld joint are limited. That is, such welding cannot be done on thinworkpieces.

When welding with embodiments of the present invention, these issues areeliminated. Because there is no welding arc being utilized there is noarc blow interference or welding current interference issues. Further,because of the precise control in heat input and depth of penetrationwhich is capable through the use of lasers, much thinner workpieces canbe welded on both sides of the weld joint at the same time.

A further exemplary embodiment of the present invention is shown in FIG.9. In this embodiment two laser beams 110 and 110A are utilized—in linewith each other—to create a unique weld profile. In the embodiment showna first beam 110 (emitted from a first laser device 120) is used tocreate first portion of a weld puddle 901 having a first cross-sectionalarea and depth, while the second beam 110A (emitted from a second laserdevice—not shown) is used to create a second portion of a weld puddle903 having a second cross-sectional area and depth, which is differentfrom the first. This embodiment can be used when it is desirable to havea portion of the weld bead having a deeper depth of penetration than theremainder of the weld bead. For example, as shown in FIG. 9 the puddle901 is made deeper and narrower than the weld puddle 903 which is madewider and shallower. Such an embodiment can be used when a deeppenetration level is needed where the work pieces meet but is notdesired for the entire portion of the weld joint.

In a further exemplary embodiment of the present invention, the firstpuddle 903 can be the weld puddle which creates the weld for the joint.This first puddle/joint is created with a first laser 120 and a fillerwire (not shown), and is made to appropriate depth of penetration. Afterthis weld joint is made a second laser (not shown) emitting a secondlaser beam 110A passes over the joint to create a second puddle 903 witha different profile where this second puddle is used to deposit anoverlay of some kind as discussed with the embodiments above. Thisoverlay will be deposited using a second filler wire, having a differentchemistry than the first filler wire. For example, embodiments of thisinvention can be used to place a corrosion resistant cladding layer overthe weld joint shortly or immediately after the joint is welded. Thiswelding operation can also be accomplished with a single laser device120 where the beam 110 is oscillated between a first beam shape/densityand a second beam shape/density to provide the desired weld puddleprofile. Thus, it is not necessary for multiple laser devices to beemployed.

As explained above, a corrosion resistant coating on the workpieces(such as galvanization), is removed during the welding process. Howeverit may be desirable to have the weld joint coated again for corrosionresistance purposes and so the second beam 110A and laser can be used toadd a corrosion resistant overlay 903, such as a cladding layer, on topof the joint 901.

Because of the various advantages of the present invention, it is alsopossible to easily join dissimilar metals via a welding operation.Joining dissimilar metals with an arc welding process is difficult. Thisdifficulty is due to many reason, including issues related tocontrolling the heat input and, therefore, the chemistry of the weldmetal which may lead to undesirable properties and defects resulting ininferior welds. This is particularly true when attempting to arc weldaluminum and steel together, which have very different meltingtemperatures, or when trying weld stainless steels to mild steel,because of their different chemistries. However, with embodiments of thepresent invention, such issues are mitigated.

FIG. 10A depicts an exemplary embodiment of this invention. Although aV-type joint is shown, the present invention is not limited in thisregard. In FIG. 10 two dissimilar metals are shown being joined at aweld joint 1000. In this example, the two dissimilar metals are aluminumand steel. In this exemplary embodiment, two different laser sources1010 and 1020 are employed. However, two laser devices are not requiredin all embodiments as a single device can be oscillated to provide thenecessary energy to melt the two different materials—this will bediscussed further below. Laser 1010 emits the beam 1011 which isdirected at the steel workpiece and the laser 1020 emits the beam 1021at the aluminum workpiece. Because each of the respective workpieces ismade from different metals or alloys they have different meltingtemperatures. As such, each of the respective laser beams 1011/1021 hasdifferent energy densities at the weld puddles 1012 and 1022. Because ofthe differing energy densities each of the respective weld puddles 1012and 1022 can be maintained at the proper size and depth. This alsoprevents excessive penetration and heat input in the workpiece with thelower melting temperature—for example, aluminum. In some embodiments,because of at least the weld joint, there is no need to have twoseparate, discrete weld puddles (as shown in FIG. 10A), rather a singleweld puddle can be formed with both work pieces, where the meltedportions of each of the workpieces form a single weld puddle. Further,if the workpieces have different chemistries but have similar meltingtemperatures, it is possible to use a single beam to irradiate bothworkpieces at the same time, with the understanding that one work piecewill melt more than the other. Further, as briefly described above, itis possible to use a single energy source (like laser device 120) toirradiate both workpieces. For example, a laser device 120 could use afirst beam shape and/or energy density to melt the first work piece andthen oscillate/change to a second beam shape and/or energy density tomelt the second work piece. The oscillation and changing of the beamcharacteristics should be accomplished at a sufficient rate to ensurethat proper melting of both workpieces is maintained so that the weldpuddle(s) are kept stable and consistent during the welding process.Other single beam embodiments can utilize a beam 110 having a shapewhich provides more heat input into one workpiece over the other toensure sufficient melting of each workpiece. In such embodiments theenergy density of the beam can be uniform for the cross-section of thebeam. For example, the beam 110 can have a trapezoidal or triangularshape so that the overall heat input into one workpiece will be lessthan other, because of the shape of the beam. Alternatively, someembodiments can use a beam 110 having a non-uniform energy distributionin its cross-section. For example, the beam 110 can have a rectangularshape (such that it impacts both workpieces) but a first region of thebeam will have a first energy density and a second region of the beam110 will have a second energy density which is different than the firstregion, so each of the regions can appropriately melt the respectiveworkpieces. As an example, the beam 110 can have a first region with ahigh energy density to melt a steel workpiece while the second regionwill have a lower energy density to melt an aluminum workpiece.

In FIG. 10A two filler wires 1030 and 1030A are shown, each beingdirected to a weld puddle 1012 and 1022, respectively. Although theembodiment shown in FIG. 10 is employing two filler wires, the presentinvention is not limited in this regard. As discussed above with respectto other embodiments, it is contemplated that only one filler wire canbe used, or more than two wires can be used, depending on the desiredweld parameters, such as the desired bead shape and deposition rate.When a single wire is employed it can be directed to either a commonpuddle (formed from the melted portions of both of the workpieces), orthe wire can be directed to only one of melted portions for integrationinto the weld joint. Thus, for example, in the embodiment shown in FIG.10A a wire can be directed to the melted portion 1022 which will then becombined with the melted portion 1012 for formation of the weld joint.Of course, if a single wire is employed it should be heated to atemperature to allow the wire to melt in the portion 1022/1012 intowhich it is being immersed.

Because dissimilar metals are being joined the chemistry of the fillerwires should be chosen to ensure that the wires can sufficiently bondwith the metals being joined. Furthermore, the composition of the fillerwire(s) should be chosen such that it has a suitable melt temperature,which allows it to melt and be consumed in the weld puddle of the lowertemperature weld puddle. In fact, it is contemplated that thechemistries of the multiple filler wires can be different to attain theproper weld chemistry. This is particularly the case when the twodifferent workpieces have material compositions where minimal admixturewill occur between the materials. In FIG. 10A, the lower temperatureweld puddle is the aluminum weld puddle 1012, and as such the fillerwire(s) 1030(A) are formulated so as to melt at a similar temperature sothat they can be easily consumed in the puddle 1012. In the exampleabove, using aluminum and steel workpieces, the filler wires can besilicon bronze, nickel aluminum bronze or aluminum bronze based wirehaving a melting temperature similar to that of the workpiece. Ofcourse, it is contemplated that the filler wire compositions should bechosen to match the desired mechanical and welding performanceproperties, while at the same time providing melting characteristicswhich are similar to that of the at least one of the workpieces to bewelded.

The following discussion, with respect to FIGS. 10B through 10C isdirected to a further exemplary embodiment where dissimilar materialsare joined. In the example discussed below, the dissimilar materials arealuminum and steel. The steel can be any one of a mild steel or astainless steel. It is understood that when joining different materialsit is desirable to minimize the creation of intermetallics, which cancreate brittle welds. Embodiments of the present invention avoid this byemploying methods and systems described herein. The weld joint shown inFIG. 10B is a typical lap joint configuration in which a steel workpiece1040 is joined to an aluminum workpiece 1041. Of course, it should benoted that while a lap joint is shown, other joints types can becreated/used with embodiments of the present invention. For example,T-joints, butt joints, and fillet joints can also be utilized. Asdescribed previously, a beam 110 is directed to the joint area to createa puddle on the steel 1040. However, unlike many of the previouslydiscussed embodiments, the beam 110 is directed only to the steel 1040so as to create the molten puddle on the steel 1040. In this embodimentthis is done because of the higher melting temperature for steel ascompared to aluminum. In some exemplary embodiments, the laser is usedto continuously heat the steel 1040 and grow the puddle until the puddlecontacts the aluminum workpiece 1041. When the puddle contacts thealuminum 1041, without direct contact from the beam 110, overmelting orpenetration of the aluminum can be avoided, while sufficient penetrationof the steel 1040 is attained. Once the puddle makes contact with thealuminum 1040 the puddle is grown to achieve a sufficient weld jointbetween the two dissimilar materials. As the puddle contacts thealuminum it melts the aluminum to obtain sufficient penetration in thealuminum while the aluminum aids in quenching or cooling the puddle. Thebeam 110 can be controlled so as to add energy to the puddle to increasethe aluminum and/or steel penetration as desired. Such a process willalso aid in minimizing puddle dilution from the aluminum workpiece,which can be disadvantageous. While some penetration into the aluminum1041 is achieved and desirable with embodiments of the presentinvention, excess penetration and dilution can be undesirable. FIG. 10Cdepicts an exemplary completed weld joint and bead.

It is generally understood that an excess mixture of aluminum and steelin the weld puddle can create intermetallics or other brittlemicrostructures, which can result in a brittle weld joint. This is oftenundesirable. Therefore, embodiments of the present invention utilize aprocess and wire which results in a weld pool/deposit that has aluminumin the range of 0.01 to 16% and iron is in the range of 0.01 to 10%. Inother exemplary embodiments, the aluminum is in the range of 11 to 14%and iron is in the range of 4 to 8%. Of course, other ranges may bepossible depending on the materials and welding conditions. However,both aluminum and iron should be present in some amount to ensure that abond is achieved—that at least some of the base materials have beenmelted, and a maximum amount should be selected to avoid the creation ofany appreciable amount of intermetallics that will degrade the weldproperties beyond an acceptable range. In some exemplary embodiments,the narrower ranges identified above ensure a sufficient bond, whileavoiding the creation of an appreciable amount of intermetallics.

The growth of the puddle can be achieved in any number of differentways, including: moving the workpieces and/or the laser beam 110;changing the size of the beam irradiation zone of the workpiece 1040;and increasing the energy input into the workpiece so as to grow thearea of the molten puddle. Of course, any combination of the above canalso be utilized to achieve the desired penetration and bead shape. Infurther embodiments, the wire 140 can also be moved during thedeposition process to cause the puddle to moved towards the aluminum1041.

Further, as described herein, at least one wire 140 is deposited intothe puddle during the welding process. As discussed above, the wire 140should be of a composition which is compatible with the dissimilarmaterials. In exemplary embodiments of the present invention, the wire140 has a composition having aluminum in the range of 6.5 to 11.5%,nickel in the range of 3 to 7%, manganese in the range of 0.7 to 3%,iron in the range of 2 to 6%, where the remaining % is copper. Inadditional exemplary embodiments of the present invention, the wire 140has a composition having aluminum in the range of 8 to 10%, nickel inthe range of 4 to 6%, manganese in the range of 1 to 2%, iron in therange of 2.5 to 4.5%, where the remaining % is copper. In furtherexemplary embodiments, the wire 140 has a composition of 9% aluminum, 5%nickel, 1.5% manganese, 3.5% iron, and the remainder is copper. Ofcourse it should be noted that the percentages and compositions statedherein contemplate the reality of manufacturing consumables and thatother elements may be present in trace amounts due to variousimpurities, etc. Thus, the percentages and compositions referencedherein contemplate that a small (trace level) percentage of theconsumable can have other elements, in addition to the copper, making upthe remainder of the consumable. In other exemplary embodiments of thepresent invention, the wire 140 can have a composition having nickel inthe range of 4 to 7%, manganese in the range of 0 to 2% and theremaining % is copper, where no aluminum or iron is intentionally addedto the composition and not present in any appreciable amount. In someexemplary embodiments of the wire 140 there is no manganese. Inexemplary embodiments, the wire 140 is to have a melting temperatureclose to the melting temperature of the steel workpiece 1040. In someexemplary embodiments, the melting temperature of the wire 140 is within10% of the melting temperature of the steel 1040 (either above orbelow). In other exemplary embodiments, the differential is in within 5%of the melting temperature of the steel. Of course, the meltingtemperature will be dictated by the composition of the consumable, andthe acceptable weld deposit chemistry. That is, in embodiments where theweld deposit can handle higher amounts of certain materials, like nickelor iron, it can be acceptable to have larger divergences in meltingtemperatures because the welding process will be able to handle largertemperatures without adversely affecting weld quality or the weldprocess.

In exemplary embodiments of the present invention, the aluminum 1041 andsteel 1040 have a similar thickness. However, this is not required asembodiments can join workpieces having different thicknesses.

Because of the methods described herein and above, embodiments of thepresent invention can provide a weld joint (as opposed to a braze joint)between aluminum and steel, where penetration is made into both thesteel and aluminum. In fact, exemplary embodiments of the presentinvention can weld aluminum and steel at welding speeds of at least 80ipm. In some exemplary embodiments, welding speeds in the range of 80 to130 ipm can be achieved with a wire 140 having a diameter in the rangeof 0.035 to 0.052″ Of course other wire diameters can also be used.

While the embodiments of FIGS. 10B and 10C have been discussed using asingle beam 110 and a single wire 140, as described otherwise herein,multiple beams and/or consumables can be used. Furthermore, in someexemplary embodiments, the beam 110 can be used to irradiate a portionof the aluminum 1041 to achieve the desired penetration, joint shape,etc. with the aluminum 1041. For example, the beam 110 can be oscillatedso as to impinge on the aluminum as desired. Of course, the beam energywill need to be controlled properly so as to not over-penetrate thealuminum 1041. For example, the energy of the beam 110 can be lessenedas it impacts the aluminum. Of course, a separate beam from a separatelaser can also be used.

It should also be noted that in some exemplary embodiments of thepresent invention, the wire 140 has a circular cross-section, liketraditional welding consumables. However, embodiments of the presentinvention are not limited in this regard and other shapes can be used.For example, the consumable 140 can have any of a polygonal, oval,elliptical or other shape. Further, the consumable 140 can also be astrip-type consumable.

Further, like other embodiments discussed herein, the welding process inaccordance with embodiments of the present invention need not utilizeshielding gas. In some applications, shielding gas can be used to aid inreducing oxidation, but in many applications it will not be necessary.

FIGS. 11A through 11C depict various embodiments of the tip 160 that canbe employed. FIG. 11A depicts a tip 160 which is very similar inconstruction and operation to that of a normal arc welding contact tip.During hot wire welding as described herein the heating current isdirected to the contact tip 160 from the power supply 170 and is passedfrom the tip 160 into the wire 140. The current is then directed throughthe wire to the workpiece via the contact of the wire 140 to theworkpiece W. This flow of current heats the wire 140 as describedherein. Of course, the power supply 170 may not be directly coupled tothe contact tip as shown but may be coupled to a wire feeder 150 whichdirects the current to the tip 160. FIG. 11B shows another embodiment ofthe present invention, where the tip 160 is comprised of two components160 and 160′, such that the negative terminal of the power supply 170 iscoupled to the second component 160′. In such an embodiment the heatingcurrent flows from the first tip component 160 to the wire 140 and theninto the second tip components 160′. The flow of the current through thewire 140, between the components 160 and 160′ causes the wire to heat asdescribed herein. FIG. 11C depicts another exemplary embodiment wherethe tip 160 contains an induction coil 1110, which causes the tip 160and the wire 140 to be heated via induction heating. In such anembodiment, the induction coil 1110 can be made integral with thecontact tip 160 or can be coiled around a surface of the tip 160. Ofcourse, other configurations can be used for the tip 160 so long as thetip deliveries the needed heating current/power to the wire 140 so thatthe wire can achieve the desired temperature for the welding operation.

The operation of exemplary embodiments of the present invention will bedescribed. As discussed above, embodiments of the present inventionemploy both a high intensity energy source and a power supply whichheats the filler wire. Each aspect of this process will be discussed inturn. It is noted that the following descriptions and discussions arenot intended to supplant or replace any of the discussions providedpreviously with respect to the previously discussed overlayingembodiments, but are intended to supplement those discussions relativeto welding or joining applications. The discussions previously regardingoverlaying operations are incorporated also for purposes of joining andwelding.

Exemplary embodiments for joining/welding can be similar to that shownin FIG. 1. As described above a hot wire power supply 170 is providedwhich provides a heating current to the filler wire 140. The currentpass from the contact tip 160 (which can be of any known construction)to the wire 140 and then into the workpiece. This resistance heatingcurrent causes the wire 140 between the tip 160 and the workpiece toreach a temperature at or near the melting temperature of the fillerwire 140 being employed. Of course, the melting temperature of thefiller wire 140 will vary depending on the size and chemistry of thewire 140. Accordingly, the desired temperature of the filler wire duringwelding will vary depending on the wire 140. As will be furtherdiscussed below, the desired operating temperature for the filler wirecan be a data input into the welding system so that the desired wiretemperature is maintained during welding. In any event, the temperatureof the wire should be such that the wire is consumed into the weldpuddle during the welding operation. In exemplary embodiments, at leasta portion of the filler wire 140 is solid as the wire enters the weldpuddle. For example, at least 30% of the filler wire is solid as thefiller wire enters the weld puddle.

In an exemplary embodiment of the present invention, the hot wire powersupply 170 supplies a current which maintains at least a portion of thefiller wire at a temperature at or above 75% of its melting temperature.For example, when using a mild steel filler wire 140 the temperature ofthe wire before it enters the puddle can be approximately 1,600° F.,whereas the wire has a melting temperature of about 2,000° F. Of course,it is understood that the respective melting temperatures and desiredoperational temperatures will varying on at least the alloy,composition, diameter and feed rate of the filler wire. In anotherexemplary embodiment, the power supply 170 maintains a portion of thefiller wire at a temperature at or above 90% of its melting temperature.In further exemplary embodiments, portions of the wire are maintained ata temperature of the wire which is at or above 95% of its meltingtemperature. In exemplary embodiments, the wire 140 will have atemperature gradient from the point at which the heating current isimparted to the wire 140 and the puddle, where the temperature at thepuddle is higher than that at the input point of the heating current. Itis desirable to have the hottest temperature of the wire 140 at or nearthe point at which the wire enters the puddle to facilitate efficientmelting of the wire 140. Thus, the temperature percentages stated aboveare to be measured on the wire at or near the point at which the wiresenters the puddle. By maintaining the filler wire 140 at a temperatureclose to or at its melting temperature the wire 140 is easily meltedinto or consumed into the weld puddle created by the heat source/laser120. That is, the wire 140 is of a temperature which does not result insignificantly quenching the weld puddle when the wire 140 makes contactwith the puddle. Because of the high temperature of the wire 140 thewire melts quickly when it makes contact with the weld puddle. It isdesirable to have the wire temperature such that the wire does notbottom out in the weld pool—make contact with the non-melted portion ofthe weld pool. Such contact can adversely affect the quality of theweld.

As described previously, in some exemplary embodiments, the completemelting of the wire 140 can be facilitated only by entry of the wire 140into the puddle. However, in other exemplary embodiments the wire 140can be completely melted by a combination of the puddle and the laserbeam 110 impacting on a portion of the wire 140. In yet otherembodiments of the present invention, the heating/melting of the wire140 can be aided by the laser beam 110 such that the beam 110contributes to the heating of the wire 140. However, because many fillerwires 140 are made of materials which can be reflective, if a reflectivelaser type is used the wire 140 should be heated to a temperature suchthat its surface reflectivity is reduced, allowing the beam 110 tocontribute to the heating/melting of the wire 140. In exemplaryembodiments of this configuration, the wire 140 and beam 110 intersectat the point at which the wire 140 enters the puddle.

As also discussed previously with regard to FIG. 1, the power supply 170and the controller 195 control the heating current to the wire 140 suchthat, during welding, the wire 140 maintains contact with the workpieceand no arc is generated. Contrary to arc welding technology, thepresence of an arc when welding with embodiments of the presentinvention can result in significant weld deficiencies. Thus, in someembodiments (as those discussed above) the voltage between the wire 140and the weld puddle should be maintained at or near 0 volts—whichindicates that the wire is shorted to or in contact with theworkpiece/weld puddle.

However, in other exemplary embodiments of the present invention it ispossible to provide a current at such a level so that a voltage levelabove 0 volts is attained without an arc being created. By utilizinghigher currents values it is possible to maintain the electrode 140 attemperatures at a higher level and closer to an electrode's meltingtemperature. This allows the welding process to proceed faster. Inexemplary embodiments of the present invention, the power supply 170monitors the voltage and as the voltage reaches or approaches a voltagevalue at some point above 0 volts the power supply 170 stops flowingcurrent to the wire 140 to ensure that no arc is created. The voltagethreshold level will typically vary, at least in part, due to the typeof welding electrode 140 being used. For example, in some exemplaryembodiments of the present invention the threshold voltage level is ator below 6 volts. In another exemplary embodiment, the threshold levelis at or below 9 volts. In a further exemplary embodiment, the thresholdlevel is at or below 14 volts, and in an additional exemplaryembodiment; the threshold level is at or below 16 volts. For example,when using mild steel filler wires the threshold level for voltage willbe of the lower type, while filler wires which are for stainless steelwelding can handle the higher voltage before an arc is created.

In further exemplary embodiments, rather than maintaining a voltagelevel below a threshold, such as above, the voltage is maintained in anoperational range. In such an embodiment, it is desirable to maintainthe voltage above a minimum amount—ensuring a high enough current tomaintain the filler wire at or near its melting temperature but below avoltage level such that no welding arc is created. For example, thevoltage can be maintained in a range of 1 to 16 volts. In a furtherexemplary embodiment the voltage is maintained in a range of 6 to 9volts. In another example, the voltage can be maintained between 12 and16 volts. Of course, the desired operational range can be affected bythe filler wire 140 used for the welding operation, such that a range(or threshold) used for a welding operation is selected, at least inpart, based on the filler wire used or characteristics of the fillerwire used. In utilizing such a range the bottom of the range is set to avoltage at which the filler wire can be sufficiently consumed in theweld puddle and the upper limit of the range is set to a voltage suchthat the creation of an arc is avoided.

As described previously, as the voltage exceeds a desired thresholdvoltage the heating current is shut off by the power supply 170 suchthat no arc is created. This aspect of the present invention will bediscussed further below.

In the many embodiments described above the power supply 170 containscircuitry which is utilized to monitor and maintain the voltage asdescribed above. The construction of such type of circuitry is known tothose in the industry. However, traditionally such circuitry has beenutilized to maintain voltage above a certain threshold for arc welding.

In further exemplary embodiments, the heating current can also bemonitored and/or regulated by the power supply 170. This can be done inaddition to monitoring voltage, power, or some level of avoltage/amperage characteristic as an alternative. That is, the currentcan be maintained at a desired level or levels to ensure that the wire140 is maintained at an appropriate temperature—for proper consumptionin the weld puddle, but yet below an arc generation current level. Forexample, in such an embodiment the voltage and/or the current are beingmonitored to ensure that either one or both are within a specified rangeor below a desired threshold. The power supply then regulates thecurrent supplied to ensure that no arc is created but the desiredoperational parameters are maintained.

In yet a further exemplary embodiment of the present invention, theheating power (V×I) can also be monitored and regulated by the powersupply 170. Specifically, in such embodiments the voltage and currentfor the heating power is monitored to be maintained at a desired level,or in a desired range. Thus, the power supply not only regulates thevoltage or current to the wire, but can regulate both the current andthe voltage. Such an embodiment may provide improved control over thewelding system. In such embodiments the heating power to the wire can beset to an upper threshold level or an optimal operational range suchthat the power is to be maintained either below the threshold level orwithin the desired range (similar to that discussed above regarding thevoltage). Again, the threshold or range settings will be based oncharacteristics of the filler wire and welding being performed, and canbe based—at least in part—on the filler wire selected. For example, itmay be determined that an optimal power setting for a mild steelelectrode having a diameter of 0.045″ is in the range of 1950 to 2,050watts. The power supply will regulate the voltage and current such thatthe power remains in this operational range. Similarly, if the powerthreshold is set at 2,000 watts, the power supply will regulate thevoltage and current so that the power level does not exceed but is closeto this threshold.

In further exemplary embodiments of the present invention, the powersupply 170 contains circuits which monitor the rate of change of theheating voltage (dv/dt), current (di/dt), and or power (dp/dt). Suchcircuits are often called premonition circuits and their generalconstruction is known. In such embodiments, the rate of change of thevoltage, current and/or power is monitored such that if the rate ofchange exceeds a certain threshold the heating current to the wire 140is turned off.

In an exemplary embodiment of the present invention, the change ofresistance (dr/dt) is also monitored. In such an embodiment, theresistance in the wire between the contact tip and the puddle ismonitored. During welding, as the wire heats up it starts to neck downand has a tendency to form an arc, during which time the resistance inthe wire increases exponentially. When this increase is detected theoutput of the power supply is turned off as described herein to ensurean arc is not created. Embodiments regulate the voltage, current, orboth, to ensure that the resistance in the wire is maintained at adesired level.

In further exemplary embodiments of the present invention, rather thanshutting off the heating current when the threshold level is detected,the power supply 170 reduces the heating current to a non-arc generationlevel. Such a level can be a background current level where no arc willbe generated if the wire is separated from the weld puddle. For example,an exemplary embodiment of the present invention can have a non-arcgeneration current level of 50 amps, where once an arc generation isdetected or predicted, or an upper threshold (discussed above) isreached, the power supply 170 drops the heating current from itsoperating level to the non-arc generation level for either apredetermined amount of time (for example, 1 to 10 ms) or until thedetected voltage, current, power, and/or resistance drops below theupper threshold. This non-arc generation threshold can be a voltagelevel, current level, resistance level, and/or a power level. In suchembodiments, by maintaining a current output during an arc generationevent—albeit at a low level—it can cause a quicker recovery to theheating current operational level.

In another exemplary embodiment of the present invention, the output ofthe power supply 170 is controlled such that no substantial arc iscreated during the welding operation. In some exemplary weldingoperations the power supply can be controlled such that no substantialarc is created between the filler wire 140 and the puddle. It isgenerally known that an arc is created between a physical gap betweenthe distal end of the filler wire 140 and the weld puddle. As describedabove, exemplary embodiments of the present invention prevent this arcfrom being created by keeping the filler wire 140 in contact with thepuddle. However, in some exemplary embodiments the presence of aninsubstantial arc will not compromise the quality of the weld. That is,in some exemplary welding operations the creation of an insubstantialarc of a short duration will not result in a level of heat input thatwill compromise the weld quality. In such embodiments, the weldingsystem and power supply is controlled and operated as described hereinwith respect to avoiding an arc completely, but the power supply 170 iscontrolled such that to the extent an arc is created the arc isinsubstantial. In some exemplary embodiments, the power supply 170 isoperated such that a created arc has a duration of less than 10 ms. Inother exemplary embodiments the arc has a duration of less than 1 ms,and in other exemplary embodiments the arc has a duration of less than300 μs. In such embodiments, the existence of such arcs does notcompromise the weld quality because the arc does not impart substantialheat input into the weld or cause significant spatter or porosity. Thus,in such embodiments the power supply 170 is controlled such that to theextent an arc is created it is kept insubstantial in duration so thatthe weld quality is not compromised. The same control logic andcomponents as discussed herein with respect to other embodiments can beused in these exemplary embodiments. However, for the upper thresholdlimit the power supply 170 can use the detection of the creation of anarc, rather than a threshold point (of current, power, voltage,resistance) below a predetermined or predicted arc creation point. Suchan embodiment can allow the welding operation to operate closer to itslimits.

Because the filler wire 140 is desired to be in a constantly shortedstate (in constant contact with the weld puddle) the current tends todecay at a slow rate. This is because of the inductance present in thepower supply, welding cables and workpiece. In some applications, it maybe necessary to force the current to decay at a faster rate such thatthe current in the wire is reduced at a high rate. Generally, the fasterthe current can be reduced the better control over the joining methodwill be achieved. In an exemplary embodiment of the present invention,the ramp down time for the current, after detection of a threshold beingreached or exceeded, is 1 millisecond. In another exemplary embodimentof the present invention, the ramp down time for the current is 300microseconds or less. In another exemplary embodiment, the ramp downtime is in the range of 300 to 100 microseconds.

In an exemplary embodiment, to achieve such ramp down times, a ramp downcircuit is introduced into the power supply 170 which aids in reducingthe ramp down time when an arc is predicted or detected. For example,when an arc is either detected or predicted a ramp down circuit opens upwhich introduces resistance into the circuit. For example, theresistance can be of a type which reduces the flow of current to below50 amps in 50 microseconds. A simplified example of such a circuit isshown in FIG. 18. The circuit 1800 has a resistor 1801 and a switch 1803placed into the welding circuit such that when the power supply isoperating and providing current the switch 1803 is closed. However, whenthe power supply stops supplying power (to prevent the creation of anarc or when an arc is detected) the switch opens forcing the inducedcurrent through the resistor 1801. The resistor 1801 greatly increasesthe resistance of the circuit and reduces the current at a quicker pace.Such a circuit type is generally known in the welding industry can befound a Power Wave® welding power supply manufactured by The LincolnElectric Company, of Cleveland, Ohio, which incorporatessurface-tension-transfer technology (“STT”). STT technology is generallydescribed in U.S. Pat. Nos. 4,866,247, 5,148,001, 6,051,810 and7,109,439, which are incorporated herein by reference in their entirety.Of course, these patents generally discuss using the disclosed circuitryto ensure that an arc is created and maintained—those skilled in theindustry can easily adapt such a system to ensure that no arc iscreated.

The above discussion can be further understood with reference to FIG.12, in which an exemplary welding system is depicted. (It should benoted that the laser system is not shown for clarity). The system 1200is shown having a hot wire power supply 1210 (which can be of a typesimilar to that shown as 170 in FIG. 1). The power supply 1210 can be ofa known welding power supply construction, such as an inverter-typepower supply. Because the design, operation and construction of suchpower supplies are known they will not be discussed in detail herein.The power supply 1210 contains a user input 1220 which allows a user toinput data including, but not limited to, wire feed speed, wire type,wire diameter, a desired power level, a desired wire temperature,voltage and/or current level. Of course, other input parameters can beutilized as needed. The user interface 1220 is coupled to aCPU/controller 1230 which receives the user input data and uses thisinformation to create the needed operational set points or ranges forthe power module 1250. The power module 1250 can be of any known type orconstruction, including an inverter or transformer type module.

The CPU/controller 1230 can determine the desired operational parametersin any number of ways, including using a lookup table, In such anembodiment, the CPU/controller 1230 utilizes the input data, forexample, wire feed speed, wire diameter and wire type to determine thedesired current level for the output (to appropriately heat the wire140) and the threshold voltage or power level (or the acceptableoperating range of voltage or power). This is because the needed currentto heat the wire 140 to the appropriate temperature will be based on atleast the input parameters. That is, an aluminum wire 140 may have alower melting temperature than a mild steel electrode, and thus requiresless current/power to melt the wire 140. Additionally, a smallerdiameter wire 140 will require less current/power than a larger diameterelectrode. Also, as the wire feed speed increases (and accordingly thedeposition rate) the needed current/power level to melt the wire will behigher.

Similarly, the input data will be used by the CPU/controller 1230 todetermine the voltage/power thresholds and/or ranges (e.g., power,current, and/or voltage) for operation such that the creation of an arcis avoided. For example, for a mild steel electrode having a diameter of0.045 inches can have a voltage range setting of 6 to 9 volts, where thepower module 1250 is driven to maintain the voltage between 6 to 9volts. In such an embodiment, the current, voltage, and/or power aredriven to maintain a minimum of 6 volts—which ensures that thecurrent/power is sufficiently high to appropriately heat theelectrode—and keep the voltage at or below 9 volts to ensure that no arcis created and that a melting temperature of the wire 140 is notexceeded. Of course, other set point parameters, such as voltage,current, power, or resistance rate changes can also be set by theCPU/controller 1230 as desired.

As shown, a positive terminal 1221 of the power supply 1210 is coupledto the contact tip 160 of the hot wire system and a negative terminal ofthe power supply is coupled to the workpiece W. Thus, a heating currentis supplied through the positive terminal 1221 to the wire 140 andreturned through the negative terminal 1222. Such a configuration isgenerally known.

Of course, in another exemplary embodiment the negative terminal 1222can also be connected to the tip 160. Since resistance heating can beused to heat the wire 140, the tip can be of a construction (as shown inFIG. 11) where both the negative and positive terminals 1221/1222 can becoupled to the contact tip 140 to heat the wire 140. For example, thecontact tip 160 can have a dual construction (as shown in FIG. 11B) oruse an induction coil (as shown in FIG. 11C).

A feedback sense lead 1223 is also coupled to the power supply 1210.This feedback sense lead can monitor voltage and deliver the detectedvoltage to a voltage detection circuit 1240. The voltage detectioncircuit 1240 communicates the detected voltage and/or detected voltagerate of change to the CPU/controller 1230 which controls the operationof the module 1250 accordingly. For example, if the voltage detected isbelow a desired operational range, the CPU/controller 1230 instructs themodule 1250 to increase its output (current, voltage, and/or power)until the detected voltage is within the desired operational range.Similarly, if the detected voltage is at or above a desired thresholdthe CPU/controller 1230 instructs the module 1250 to shut off the flowof current to the tip 160 so that an arc is not created. If the voltagedrops below the desired threshold the CPU/controller 1230 instructs themodule 1250 to supply a current or voltage, or both to continue thewelding process. Of course, the CPU/controller 1230 can also instructthe module 1250 to maintain or supply a desired power level.

It is noted that the detection circuit 1240 and CPU/controller 1230 canhave a similar construction and operation as the controller 195 shown inFIG. 1. In exemplary embodiments of the present invention, thesampling/detection rate is at least 10 KHz. In other exemplaryembodiments, the detection/sampling rate is in the range of 100 to 200KHz.

FIGS. 13A-C depict exemplary current and voltage waveforms utilized inembodiments of the present invention. Each of these waveforms will bediscussed in turn. FIG. 13A shows the voltage and current waveforms foran embodiment where the filler wire 140 touches the weld puddle afterthe power supply output is turned back on—after an arc detection event.As shown, the output voltage of the power supply was at some operationallevel below a determined threshold (9 volts) and then increases to thisthreshold during welding. The operational level can be a determinedlevel based on various input parameters (discussed previously) and canbe a set operational voltage, current and/or power level. Thisoperational level is the desired output of the power supply 170 for agiven welding operation and is to provide the desired heating signal tothe filler wire 140. During welding, an event may occur which can leadto the creation of an arc. In FIG. 13A the event causes an increase inthe voltage, causing it to increase to point A. At point A the powersupply/control circuitry hits the 9 volt threshold (which can be an arcdetection point or simply a predetermined upper threshold, which can bebelow an arc creation point) and turns off the output of the powersupply causing the current and voltage to drop to a reduced level atpoint B. The slope of the current drop can be controlled by theinclusion of a ramp down circuit (as discussed herein) which aids inrapidly reducing the current resultant from the system inductance. Thecurrent or voltage levels at point B can be predetermined or they can bereached after a predetermined duration in time. For example, in someembodiments, not only is an upper threshold for voltage (or current orpower) set for welding, but also a lower non-arc generation level. Thislower level can be either a lower voltage, current, or power level atwhich it is ensured that no arc can be created such that it isacceptable to turn back on the power supply and no arc will be created.Having such a lower level allows the power supply to turn back onquickly and ensure that no arc is created. For example, if a powersupply set point for welding is set at 2,000 watts, with a voltagethreshold of 11 volts, this lower power setting can be set at 500 watts.Thus, when the upper voltage threshold (which can also be a current orpower threshold depending on the embodiment) is reached the output isreduced to 500 watts. (This lower threshold can also be a lower currentor voltage setting, or both, as well). Alternatively, rather thansetting a lower detection limit a timing circuit can be utilized to turnbegin supplying current after a set duration of time. In exemplaryembodiments of the present invention, such duration can be in the rangeof 500 to 1000 ms. In FIG. 13A, point C represents the time the outputis again being supplied to the wire 140. It is noted that the delayshown between point B and C can be the result of an intentional delay orcan simply be a result of system delay. At point C current is againbeing supplied to heat the filler wire. However, because the filler wireis not yet touching the weld puddle the voltage increases while thecurrent does not. At point D the wire makes contact with the puddle andthe voltage and current settle back to the desired operational levels.As shown, the voltage may exceed the upper threshold prior to contact atD, which can occur when the power source has an OCV level higher thanthat of the operating threshold. For example, this higher OCV level canbe an upper limit set in the power supply as a result of its design ormanufacture.

FIG. 13B is similar to that described above, except that the filler wire140 is contacting the weld puddle when the output of the power supply isincreased. In such a situation either the wire never left the weldpuddle or the wire was contacted with the weld puddle prior to point C.FIG. 13B shows points C and D together because the wire is in contactwith the puddle when the output is turned back on. Thus both the currentand voltage increase to the desired operational setting at point E.

FIG. 13C is an embodiment where there is little or no delay between theoutput being turned off (point A) and being turned back on (point B),and the wire is in contact with the puddle some time prior to point B.The depicted waveforms can be utilized in embodiments described abovewhere a lower threshold is set such that when the lower threshold isreached—whether it's current, power, or voltage—the output is turnedback on with little or no delay. It is noted that this lower thresholdsetting can be set using the same or similar parameters as theoperational upper thresholds or ranges as described herein. For example,this lower threshold can be set based on wire composition, diameter,feed speed, or various other parameters described herein. Such anembodiment can minimize delay in returning to the desired operationalset points for welding and can minimize any necking that may occur inthe wire. The minimization of necking aids in minimizing the chances ofan arc being created.

FIG. 14 depicts yet another exemplary embodiment of the presentinvention. FIG. 14 shows an embodiment similar to that as shown inFIG. 1. However, certain components and connections are not depicted forclarity. FIG. 14 depicts a system 1400 in which a thermal sensor 1410 isutilized to monitor the temperature of the wire 140. The thermal sensor1410 can be of any known type capable of detecting the temperature ofthe wire 140. The sensor 1410 can make contact with the wire 140 or canbe coupled to the tip 160 so as to detect the temperature of the wire.In a further exemplary embodiment of the present invention, the sensor1410 is a type which uses a laser or infrared beam which is capable ofdetecting the temperature of a small object—such as the diameter of afiller wire—without contacting the wire 140. In such an embodiment thesensor 1410 is positioned such that the temperature of the wire 140 canbe detected at the stick out of the wire 140—that is at some pointbetween the end of the tip 160 and the weld puddle. The sensor 1410should also be positioned such that the sensor 1410 for the wire 140does not sense the weld puddle temperature.

The sensor 1410 is coupled to the sensing and control unit 195(discussed with regard to FIG. 1) such that temperature feed backinformation can be provided to the power supply 170 and/or the laserpower supply 130 so that the control of the system 1400 can beoptimized. For example, the power or current output of the power supply170 can be adjusted based on at least the feedback from the sensor 1410.That is, in an embodiment of the present invention either the user caninput a desired temperature setting (for a given weld and/or wire 140)or the sensing and control unit can set a desired temperature based onother user input data (wire feed speed, electrode type, etc.) and thenthe sensing and control unit 195 would control at least the power supply170 to maintain that desired temperature.

In such an embodiment it is possible to account for heating of the wire140 that may occur due to the laser beam 110 impacting on the wire 140before the wire enters the weld puddle. In embodiments of the inventionthe temperature of the wire 140 can be controlled only via power supply170 by controlling the current in the wire 140. However, in otherembodiments at least some of the heating of the wire 140 can come fromthe laser beam 110 impinging on at least a part of the wire 140. Assuch, the current or power from the power supply 170 alone may not berepresentative of the temperature of the wire 140. As such, utilizationof the sensor 1410 can aid in regulating the temperature of the wire 140through control of the power supply 170 and/or the laser power supply130.

In a further exemplary embodiment (also shown in FIG. 14) a temperaturesensor 1420 is directed to sense the temperature of the weld puddle. Inthis embodiment the temperature of the weld puddle is also coupled tothe sensing and control unit 195. However, in another exemplaryembodiment, the sensor 1420 can be coupled directly to the laser powersupply 130. Feedback from the sensor 1420 is used to control output fromlaser power supply 130/laser 120. That is, the energy density of thelaser beam 110 can be modified to ensure that the desired weld puddletemperature is achieved.

In yet a further exemplary embodiment of the invention, rather thandirecting the sensor 1420 at the puddle, it can be directed at an areaof the workpiece adjacent the weld puddle. Specifically, it may bedesirable to ensure that the heat input to the workpiece adjacent theweld is minimized. The sensor 1420 can be positioned to monitor thistemperature sensitive area such that a threshold temperature is notexceeded adjacent the weld. For example, the sensor 1420 can monitor theworkpiece temperature and reduce the energy density of the beam 110based on the sensed temperature. Such a configuration would ensure thatthe heat input adjacent the weld bead would not exceed a desiredthreshold. Such an embodiment can be utilized in precision weldingoperations where heat input into the workpiece is critical.

In another exemplary embodiment of the present invention, the sensingand control unit 195 can be coupled to a feed force detection unit (notshown) which is coupled to the wire feeding mechanism (not shown—but see150 in FIG. 1). The feed force detection units are known and detect thefeed force being applied to the wire 140 as it is being fed to theworkpiece 115. For example, such a detection unit can monitor the torquebeing applied by a wire feeding motor in the wire feeder 150. If thewire 140 passes through the molten weld puddle without fully melting itwill contact a solid portion of the workpiece and such contact willcause the feed force to increase as the motor is trying to maintain aset feed rate. This increase in force/torque can be detected and relayedto the control 195 which utilizes this information to adjust thevoltage, current and/or power to the wire 140 to ensure proper meltingof the wire 140 in the puddle.

It is noted that in some exemplary embodiments of the present invention,the wire is not constantly fed into the weld puddle, but can be done sointermittently based on a desired weld profile. Specifically, theversatility of various embodiments of the present invention allowseither an operator or the control unit 195 to start and stop feeding thewire 140 into the puddle as desired. For example, there are manydifferent types of complex weld profiles and geometry that may have someportions of the weld joint which require the use of a filler metal (thewire 140) and other portions of the same joint or on the same workpiecethat do not require the use of filler metal. As such, during a firstportion of a weld the control unit 195 can operate only the laser 120 tocause a laser weld of this first portion of the joint, but when thewelding operation reaches a second portion of the welding joint—whichrequires the use of a filler metal—the controller 195 causes the powersupply and 170 and the wire feeder 150 to begin depositing the wire 140into the weld puddle. Then, as the welding operation reaches the end ofthe second portion the deposition of the wire 140 can be stopped. Thisallows for the creation of continuous welds having a profile whichsignificantly varies from one portion to the next. Such capabilityallows a workpiece to be welded in a single welding operation as opposedto having many discrete welding operations. Of course, many variationscan be implemented. For example, a weld can have three or more distinctportions requiring a weld profile with varying shape, depth and fillerrequirements such that the use of the laser and the wire 140 can bedifferent in each weld portion. Furthermore, additional wires can beadded or removed as needed as well. That is, a first weld portion mayneed only a laser weld while a second portion only requires the use of asingle filler wire 140, and a final portion of the weld requires the useof two or more filler wires. The controller 195 can be made capable tocontrol the various system components to achieve such a varying weldprofile in a continuous welding operation, such that a continuous weldbead is created in a single weld pass.

FIG. 15 depicts a typical weld puddle P when welding in accordance withexemplary embodiments of the present invention. As described previouslythe laser beam 110 creates the puddle P in the surface of the workpieceW. The weld puddle has a length L which is a function of the energydensity, shape and movement of the beam 110. In an exemplary embodimentof the present invention, the beam 110 is directed to the puddle P at adistance Z from the trailing edge of the weld puddle. In suchembodiments, the high intensity energy source (e.g., the laser 120) doescause its energy to directly impinge on the filler wire 140 such thatthe energy source 120 does not melt the wire 140, rather the wire 140completes its melting because of its contact with the weld puddle. Thetrailing edge of the puddle P can be generally defined as the point atwhich the molten puddle ends and the weld bead WB created begins itssolidification. In an embodiment of the present invention the distance Zis 50% of the length L of the puddle P. In a further exemplaryembodiment, the distance Z is in the range of 40 to 75% the length L ofthe puddle P.

The filler wire 140 impacts the puddle P behind the beam 110—in thetravel direction of the weld—as shown in FIG. 15. As shown the wire 140impacts the puddle P as distance X before the trailing edge of thepuddle P. In an exemplary embodiment, the distance X is in the range of20 to 60% of the length of the puddle P. In another exemplaryembodiment, the distance X is in the range of 30 to 45% of the length Lof the puddle P. In other exemplary embodiments, the wire 140 and thebeam 110 intersect at the surface of or at a point above the puddle Psuch that at least some of the beam 110 impinges on the wire 140 duringthe welding process. In such an embodiment the laser beam 110 isutilized to aid in the melting of the wire 140 for deposition in thepuddle P. Using the beam 110 to aid in the melting of the wire 140 aidsin preventing the wire 140 from quenching the puddle P if the wire 140is too cool to be quickly consumed in the puddle P. However, as statedpreviously in some exemplary embodiments (as shown in FIG. 15) theenergy source 120 and beam 110 do not appreciably melt any portion ofthe filler wire 140 as the melting is completed by the heat of the weldpuddle.

In the embodiment shown in FIG. 15 the wire 140 trails the beam 110 andis in line with the beam 110. However, the present invention is notlimited to this configuration as the wire 140 can lead (in the traveldirection). Further, it is not necessary to have the wire 140 in linewith the beam in the travel direction, but the wire can impinge thepuddle from any direction so long as suitable wire melting occurs in thepuddle.

FIGS. 16A through 16F depict various puddles P with the footprint of thelaser beam 110 depicted. As shown, in some exemplary embodiments thepuddle P has a circular footprint. However, embodiments of the inventionare not limited to this configuration. For example, it is contemplatedthat the puddle can have elliptical or other shapes as well.

Further, in FIGS. 16A-16F the beam 110 is shown having a circularcross-section. Again, other embodiments of the present invention are notlimited in this regard as the beam 110 can have an elliptical,rectangular, or other shape so as to effectively create a weld puddle P.

In some embodiments, the laser beam 110 can remain stationary withrespect to the weld puddle P. That is, the beam 110 remains in arelatively consistent position with respect to the puddle P duringwelding. However, other embodiments are not limited in such a way, asexemplified in FIGS. 16A-16D. For example, FIG. 16A depicts anembodiment where the beam 110 is translated in a circular pattern aroundthe weld puddle P. In this figure the beam 110 translates such that atleast one point on the beam 110 overlaps the center C of the puddle atall times. In another embodiment, a circular pattern is used but thebeam 110 does not contact the center C. FIG. 16B depicts an embodimentwhere the beam is translated back-and-forth along a single line. Thisembodiment can be used to either elongate or widen the puddle Pdepending on the desired puddle P shape. FIG. 16C depicts an embodimentwhere the two different beam cross-sections are used. The first beamcross-section 110 has a first geometry and the second beam cross-section110′ has a second cross-section. Such an embodiment can be used toincrease penetration at a point in the puddle P while still maintaininga larger puddle size—if needed. This embodiment can be accomplished witha single laser 120 by changing the beam shape through the use of thelaser lenses and optics, or can be accomplished through the use ofmultiple lasers 120. FIG. 16D depicts a beam 110 being translated in anelliptical pattern in the puddle P. Again, such a pattern can be used toeither elongate or widen the weld puddle P as needed. Other beam 110translations can be utilized to create the puddle P.

FIGS. 16E and 16F depict a cross-section of a workpiece W and puddle Pusing different beam intensities. FIG. 16E depicts a shallow widerpuddle P which is created by a wider beam 110, while FIG. 16F depicts adeeper and narrow weld puddle P—typically referred to as a “keyhole”. Inthis embodiment, the beam is focused such that its focal point is nearthe upper surface of the workpiece W. With such a focus the beam 110 isable to penetrate through the full depth of the workpiece and aid increating a back bead BB on the bottom surface of the workpiece W. Thebeam intensity and shape are to be determined based on the desiredproperties of the weld puddle during welding.

The laser 120 can be moved, translated or operated via any known methodsand devices. Because the movement and optics of lasers are generallyknown, they will not be discussed in detail herein. FIG. 17 depicts asystem 1700 in accordance with an exemplary embodiment of the presentinvention, where the laser 120 can be moved and have its optics (such asits lenses) changed or adjusted during operation. This system 1700couples the sensing and control unit 195 to both a motor 1710 and anoptics drive unit 1720. The motor 1710 moves or translates the laser 120such that the position of the beam 110 relative to the weld puddle ismoved during welding. For example, the motor 1710 can translate the beam110 back and forth, move it in a circular pattern, etc. Similarly, theoptics drive unit 1720 receives instructions from the sensing andcontrol unit 195 to control the optics of the laser 120. For example,the optics drive unit 1720 can cause the focal point of the beam 110 tomove or change relative to the surface of the workpiece, thus changingthe penetration or depth of the weld puddle. Similarly, the optics driveunit 1720 can cause the optics of the laser 120 to change the shape ofthe beam 110. As such, during welding the sensing and control unit 195control the laser 120 and beam 110 to maintain and/or modify theproperties of the weld puddle during operation.

In each of FIGS. 1, 14 and 17 the laser power supply 130, hot wire powersupply 170 and sensing and control unit 195 are shown separately forclarity. However, in embodiments of the invention these components canbe made integral into a single welding system. Aspects of the presentinvention do not require the individually discussed components above tobe maintained as separately physical units or stand alone structures.

As described above, the high intensity energy source can be any numberof energy sources, including welding power sources. An exemplaryembodiment of this is shown in FIG. 20, which shows a system 2000similar to the system 100 shown in FIG. 1. Many of the components of thesystem 2000 are similar to the components in the system 100, and as suchtheir operation and utilization will not be discussed again in detail.However, in the system 2000 the laser system is replaced with an arcwelding system, such as a GMAW system. The GMAW system includes a powersupply 2130, a wire feeder 2150 and a torch 2120. A welding electrode2110 is delivered to a molten puddle via the wire feeder 2150 and thetorch 2120. The operation of a GMAW welding system of the type describedherein is well known and need not be described in detail herein. Itshould be noted that although a GMAW system is shown and discussedregarding depicted exemplary embodiments, exemplary embodiments of thepresent invention can also be used with GTAW, FCAW, MCAW, and SAWsystems, cladding systems, brazing systems, and combinations of thesesystems, etc., including those systems that use an arc to aid in thetransfer of a consumable to a molten puddle on a workpiece. Not shown inFIG. 20 is a shielding gas system or sub arc flux system which can beused in accordance with known methods.

Like the laser systems described above, the arc generation systems (thatcan be used as the high intensity energy source) are used to create themolten puddle to which the hot wire 140 is added using systems andembodiments as described in detail above. However, with the arcgeneration systems, as is known, an additional consumable 2110 is alsoadded to the puddle. This additional consumable adds to the alreadyincreased deposition performance provided by the hot wire processdescribed herein. This performance will be discussed in more detailbelow.

Further, as is generally known arc generation systems, such as GMAW usehigh levels of current to generate an arc between the advancingconsumable and the molten puddle on the workpiece. Similarly, GTAWsystems use high current levels to generate an arc between an electrodeand the workpiece, into which a consumable is added. As is generallyknown, many different current waveforms can be utilized for a GTAW orGMAW welding operation, such as constant current, pulse current, etc.However, during operation of the system 2000 the current generated bythe power supply 2130 can interfere with the current generated by thepower supply 170 which is used to heat the wire 140. Because the wire140 is proximate to the arc generated by the power supply 2130 (becausethey are each directed to the same molten puddle, similar to thatdescribed above) the respective currents can interfere with each other.Specifically, each of the currents generates a magnetic field and thosefields can interfere with each other and adversely affect theiroperation. For example, the magnetic fields generated by the hot wirecurrent can interfere with the stability of the arc generated by thepower supply 2130. That is, without proper control and synchronizationbetween the respective currents the competing magnetic fields candestabilize the arc and thus destabilize the process. Therefore,exemplary embodiments utilize current synchronization between the powersupplies 2130 and 170 to ensure stable operation, which will bediscussed further below.

FIG. 21 depicts a closer view of an exemplary welding operation of thepresent invention. As can be seen the torch 2120 (which can be anexemplary GMAW/MIG torch) delivers a consumable 2110 to a weld puddle WPthrough the use of an arc—as is generally known. Further, the hot wireconsumable 140 is delivered to the weld puddle WP in accordance with anyof the embodiments described above. It should be noted that although thetorch 2120 and tip 160 are shown separately in this figure, thesecomponents can be made integrally into a single torch unit whichdelivers both consumables 2110 and 140 to the puddle. Of course, to theextent an integral construction is utilized, electrical isolation withinthe torch must be used so as to prevent current transfer between theconsumables during the process. As stated above, magnetic fields inducedby the respective currents can interfere with each other and thusembodiments of the present invention synchronize the respectivecurrents. Synchronization can be achieved via various methods. Forexample, the sensing and current controller 195 can be used to controlthe operation of the power supplies 2130 and 170 to synchronize thecurrents. Alternatively a master-slave relationship can also be utilizedwhere one of the power supplies is used to control the output of theother. The control of the relative currents can be accomplished by anumber of methodologies including the use of state tables or algorithmsthat control the power supplies such that their output currents aresynchronized for a stable operation. This will be discussed relative toFIGS. 22A-C. For example, a dual-state based system and devices similarto that described in US Patent Publication No. 2010/0096373 can beutilized. US Patent Publication No. 2010/0096373, published on Apr. 22,2010, is incorporated herein by reference in its entirety.

Each of FIGS. 22A-C depicts exemplary current waveforms. FIG. 22Adepicts an exemplary welding waveform (either GMAW or GTAW) which usescurrent pulses 2202 to aid in the transfer of droplets from the wire2110 to the puddle. Of course, the waveform shown is exemplary andrepresentative and not intended to be limiting, for example the currentwaveforms can be that for pulsed spray transfer, pulse welding, surfacetension transfer welding, etc. The hot wire power supply 170 outputs acurrent waveform 2203 which also has a series of pulses 2204 to heat thewire 140, through resistance heating as generally described above. Thecurrent pulses 2204 are separated by a background level of a lessercurrent level. As generally described previously, the waveform 2203 isused to heat the wire 140 to at or near its melting temperature and usesthe pulses 2204 and background to heat the wire 140 through resistanceheating. As shown in FIG. 22A the pulses 2202 and 2204 from therespective current waveforms are synchronized such that they are inphase with each other. In this exemplary embodiment, the currentwaveforms are controlled such that the current pulses 2202/2204 have asimilar, or the same, frequency and are in phase with each other asshown. Surprisingly, it was discovered that having the waveforms inphase produces a stable and consistent operation, where the arc is notsignificantly interfered with by the heating current generated by thewaveform 2203.

FIG. 22B depicts waveforms from another exemplary embodiment of thepresent invention. In this embodiment, the heating current waveform 2205is controlled/synchronized such that the pulses 2206 are out-of-phasewith the pulses 2202 by a constant phase angle Θ. In such an embodiment,the phase angle is chosen to ensure stable operation of the process andto ensure that the arc is maintained in a stable condition. In exemplaryembodiments of the present invention, the phase angle Θ is in the rangeof 30 to 90 degrees. In other exemplary embodiments, the phase angle is0 degrees. Of course, other phase angles can be utilized so as to obtainstable operation, and can be in the range of 0 to 360 degrees, while inother exemplary embodiments the phase angle is in the range of 0 and 180degrees.

FIG. 22C depicts another exemplary embodiment of the present invention,where the hot wire current 2207 is synchronized with the weldingwaveform 2201 such that the hot wire pulses 2208 are out-of phase suchthat the phase angle Θ is about 180 degrees with the welding pulses2202, and occurring only during the background portion 2210 of thewaveform 2201. In this embodiment the respective currents are notpeaking at the same time. That is, the pulses 2208 of the waveform 2207begin and end during the respective background portions 2210 of thewaveform 2201.

In some exemplary embodiments of the present invention, the pulse widthof the welding and hot-wire pulses is the same. However, in otherembodiments, the respective pulse-widths can be different. For example,when using a GMAW pulse waveform with a hot wire pulse waveform, theGMAW pulse width is in the range of 1.5 to 2.5 milliseconds and thehot-wire pulse width is in the range of 1.8 to 3 milliseconds, and thehot wire pulse width is larger than that of the GMAW pulse width.

It should be noted that although the heating current is shown as apulsed current, for some exemplary embodiments the heating current canbe constant power as described previously. The hot-wire current can alsobe a pulsed heating power, constant voltage, a sloped output and/or ajoules/time based output.

As explained herein, to the extent both currents are pulsed currentsthey are to be synchronized to ensure stable operation. There are manymethods that can be used to accomplish this, including the use ofsynchronization signals. For example, the controller 195 (which can beintegral to either or the power supplies 170/2130) can set asynchronization signal to start the pulsed arc peak and also set thedesired start time for the hot wire pulse peak. As explained above, insome embodiments, the pulses will be synchronized to start at the sametime, while in other embodiments the synchronization signal can set thestart of the pulse peak for the hot wire current at some duration afterthe arc pulse peak—the duration would be sufficient to obtained thedesired phase angle for the operation.

FIG. 23 represents another exemplary embodiment of the presentinvention. In this embodiment a GTAW welding/coating operation isutilized where a GTAW torch 2121 and an electrode 2122 create an arcinto which a consumable 2120 is delivered. Again the arc and the hotwire 140 are delivered to the same puddle WP to create a bead WB asshown. The operation of a GTAW embodiment is similar to that describedabove, in that the arc and the hot wire 140 are interacting with thesame weld puddle WP. Again, as with the above described GMAW operationthe current used to generate the arc in the GTAW operation issynchronized with the current for the hot wire operation. For example,the pulse relationship can be used as shown in FIGS. 22A to 22C.Further, the controller 195 can control the synchronization between thepower supplies using a dual-state table, or other similar methods ofcontrol. It should be noted that the consumable 2120 can be delivered tothe weld as a cold wire or can also be a hot-wire consumable. That is,both consumables 2110 and 140 can be heated as described herein.Alternatively, only one of the consumables 2120 and 140 can be thehot-wire as described herein.

In either of the GTAW or GMAW type embodiments discussed above(including the use of other arc type methods) the arc is positioned inthe lead—relative to the travel direction. This is shown in each ofFIGS. 21 and 23. This is because the arc is used to achieve the desiredpenetration in the workpiece(s). That is, the arc is used to create themolten puddle and achieve the desired penetration in the workpiece(s).Then, following behind the arc process is the hot wire process, which isdescribed in detail herein. The addition of the hot wire process addsmore consumable 140 to the puddle without the additional heat input ofanother welding arc, such as in a traditional tandem MIG process inwhich at least two arcs are used. Thus, embodiments of the presentinvention can achieve significant deposition rates at considerably lessheat input than known tandem welding methods.

As shown in FIG. 21, the hot wire 140 is inserted in the same weldpuddle WP as the arc, but trails behind the arc by a distance D. In someexemplary embodiments, this distance is in the range of 5 to 20 mm, andin other embodiments, this distance is in the range of 5 to 10 mm. Ofcourse, other distances can be used so long as the wire 140 is fed intothe same molten puddle as that created by the leading arc. However, thewires 2110 and 140 are to be deposited in the same molten puddle and thedistance D is to be such that there is minimal magnetic interferencewith the arc by the heating current used to heat the wire 140. Ingeneral, the size of the puddle—into which the arc and the wire arecollectively directed—will depend on the welding speed, arc parameters,total power to the wire 140, material type, etc., which will also befactors in determining a desired distance between wires 2110 and 140.

It should be noted that the operation of the hot wire current (e.g.,2203, 2203, or 2207) is similar to that described in detail herein whenan arc event is detected or predicted by either the controller 195 orthe power supply 170. That is, even though the current is pulsed thecurrent can be shut off or minimized as described herein if an arc iscreated or detected. Furthermore, in some exemplary embodiments, thebackground portions 2211 have a current level below an arc generationlevel for the wire 140 (which can be determined by the controller 195based on user input information), and rather than shutting the hot wirecurrent off when an arc is detected the power supply 170 can drop thecurrent to the background level 2211 for a duration or until it isdetermined that the arc is extinguished or will not occur (as generallydescribed previously). For example, the power supply 170 can skip apredetermined number of pulses 2203/2205/2207 or just not pulse for aduration, such as 10 to 100 ms, after which time the power supply 170can start the pulses again to heat the wire 140 to the appropriatetemperature.

As stated above, because at least two consumables 140/2110 are used inthe same puddle a very high deposition rate can be achieved, with a heatinput which is similar to that of a single arc operation. This providessignificant advantages over tandem MIG welding systems which have veryhigh heat input into the workpiece. For example, embodiments of thepresent invention can easily achieve at least 23 lb/hr deposition ratewith the heat input of a single arc. Other exemplary embodiments have adeposition rate of at least 35 lb/hr.

In exemplary embodiments of the present invention, each of the wires 140and 2110 are the same, in that they have the same composition, diameter,etc. However, in other exemplary embodiments the wires can be different.For example, the wires can have different diameters, wire feed speedsand composition as desired for the particular operation. In an exemplaryembodiment the wire feed speed for the lead wire 2110 is higher thanthat for the hot wire 140. For example, the lead wire 2110 can have awire feed speed of 450 ipm, while the trail wire 140 has a wire feedspeed of 400 ipm. Further, the wires can have different size andcompositions. In fact, because the hot wire 140 does not have to travelthrough an arc to be deposited into the puddle the hot wire 140 can havematerials/components which typically do not transfer well through anarc. For example, the wire 140 can have a tungsten carbide, or othersimilar hard facing material, which cannot be added to a typical weldingelectrode because of the arc. Additionally, the leading electrode 2110can have a composition which is rich in wetting agents, which can helpwetting the puddle to provide a desired bead shape. Further, the hotwire 140 can also contain slag elements which will aid in protecting thepuddle. Therefore, embodiments of the present invention allow for greatflexibility in the weld chemistry. It should be noted that because thewire 2110 is the lead wire, the arc welding operation, with the leadwire, provides the penetration for the weld joint, where the hot wireprovides additional fill for the joint.

In some exemplary embodiments of the present invention, the combinationof the arc and the hot-wire can be used to balance the heat input to theweld deposit, consistent with the requirements and limitations of thespecific operation to be performed. For example, the heat from the leadarc can be increased for joining applications where the heat from thearc aids in obtaining the penetration needed to join the workpieces andthe hot-wire is primarily used for fill of the joint. However, incladding or build-up processes, the hot-wire wire feed speed can beincreased to minimize dilution and increase build up.

Further, because different wire chemistries can be used a weld joint canbe created having different layers, which is traditionally achieved bytwo separate passes. The lead wire 2110 can have the required chemistryneeded for a traditional first pass, while the trail wire 140 can havethe chemistry needed for a traditional second pass. Further, in someembodiments at least one of the wires 140/2110 can be a cored wire. Forexample the hot wire 140 can be a cored wire having a powder core whichdeposits a desired material into the weld puddle.

FIG. 24 depicts another exemplary embodiment of current waveforms of thepresent invention. In this embodiment, the hot wire current 2403 is anAC current which is synchronized with the welding current 2401 (whetherit be GMAW or GTAW). In this embodiment, the positive pulses 2404 of theheating current are synchronized with the pulses 2402 of the current2401, while the negative pulses 2405 of the heating current 2403 aresynchronized with the background portions 2406 of the welding current.Of course, in other embodiments the synchronization can be opposite, inthat the positive pulses 2404 are synchronized with the background 2406and the negative pulses 2405 are synchronized with the pulses 2402. Inanother embodiment, there is a phase angle between the pulsed weldingcurrent and the hot wire current. By utilizing an AC waveform 2403 thealternating current (and thus alternating magnetic field) can be used toaid in stabilizing the arc. Of course, other embodiments can be utilizedwithout departing from the spirit or scope of the present invention. Forexample, in a system using a submerged arc welding (SAW) operation, theSAW current waveform can be an AC waveform and the hot wire currentwaveform is an AC or a pulsed DC power waveform, where each of thewaveforms are synchronized with each other.

It is also noted that embodiments of the present invention can be usedwhere the welding current is a constant or near constant currentwaveform. In such embodiments, an alternating heating current 2403 canbe used to maintain the stability of the arc. The stability is achievedby the constantly changed magnetic field from the heating current 2403.

FIG. 25 depicts another exemplary embodiment of the present invention,where the hot wire 140 is positioned between two tandem arc weldingoperations. In FIG. 25 the arc welding operations are depicted as GMAWtype welding, but can also be GTAW, FCAW, MCAW or SAW type systems. Inthe figures, the lead torch 2120 is coupled to a first power supply 2130and delivers a first electrode 2110 to the puddle via an arc weldingoperation. Trailing the lead arc is the hot wire 140 (which is depositedas discussed above). Trailing the hot wire 140 is a trailing arc weldingoperation using a second power supply 2130′, a second torch 2120′ and asecond arc welding wire 2110′. Thus, the configuration is similar tothat of a tandem GMAW welding system but has a hot-wire 140 depositedinto the common puddle between the torches 2120 and 2120′. Such anembodiment further increases the deposition rate of materials into thepuddle. It should be noted that embodiments of the present invention canuse additional welding torches and/or hot wire consumables in a singleoperation, and are not limited to the embodiments shown in the Figures.For example, more than hot-wire can be used to deposit additionalmaterials into the puddle during a single pass. As mentioned above, SAWprocesses can be used rather than the GMAW processes generally discussedherein. For example, the embodiment shown in FIG. 25 can utilize leadingand trailing SAW processes with a similar configuration as to that shownin this figure. Of course, rather than a shielding gas, a granular fluxwould be used to shield the arcs. The overall method or operation andcontrol, as discussed above, are similarly applicable when using otherwelding methodologies, such as SAW. For example, FIG. 25A depictsexemplary waveforms that can be used in an SAW system with a hot-wire asdescribed herein. As depicted, the lead SAW current waveform 2501 is anAC waveform having a plurality of positive pulses 2503 and a pluralityof negative pulses 2505, while the trailing SAW current 2521 is also anAC waveform having a plurality of positive pulses 2523 and a pluralityof negative pulses 2525, where the trailing waveform 2521 isout-of-phase from the leading waveform 2501 by a phase angle α. Inexemplary embodiments of the present invention, the phase angle α is inthe range of 90 to 270 degrees. It is also noted that in the embodimentshown the +/− offset between the waveforms 2501 and 2521 is different inthat the trailing waveform 2521 has a larger negative offset than theleading waveform 2501. In other exemplary embodiments, the offset can bethe same, or can be reversed. The hot wire current 2510 shown in a pulsecurrent having a plurality of positive pulses 2511 separated by abackground level 2513 where the waveform 2510 has an offset phase angleθ, which is different than the phase angle α. In an exemplaryembodiment, the hot wire phase angle θ is in the range of 45 to 315degrees, but is different than the phase angle α.

It is noted that although the above discussion was directed to a SAWtype operation, other exemplary embodiments using a similarsynchronization methodology can be of a GMAW, FCAW, MCAW, or GTAW typeoperation, or a combination thereof.

As stated above, embodiments of the present invention can greatlyincrease the deposition of materials into the puddle while keeping thetotal heat input lower than traditional tandem systems. However, someexemplary embodiments can create a weld bead WB shape which is higherthan traditional tandem methods. That is, the weld bead WB tends tostand up higher above the surface of the workpiece and does not wet outto the sides of the weld bead WB as much as tandem systems. Generally,this is because the hot wire 140 will aid in quenching the puddlefollowing the leading arc welding operation. Therefore, some exemplaryembodiments of the present invention utilize systems and components toaid in widening or wetting out the puddle during a welding/coatingoperation.

FIG. 26 depicts an exemplary embodiment, where two GMAW torches 2120 and2120′ are not positioned in line, but are rather positioned in aside-by-side position—as shown, where the hot wire 140 is trailingbehind the two torches 2120/2120′. In this embodiment, having the twoGMAW arcs in a side-by-side configuration will widen the puddle WP andaid in wetting out the puddle to flatten the weld bead WB. As with theother embodiments, the hot wire 140 trails the arc welding operation andcan be positioned on the center-line of the weld bead WB behind the arcwelding operations. However, its is not necessary that the hot wire 140remain in the centerline as the hot wire can be oscillated or movedrelative to the puddle during the welding operation.

FIG. 27 depicts another exemplary embodiment where lasers 2720 and 2720′are used on either side of the weld puddle WP to help flatten out thepuddle or aid in the wetting of the puddle. The lasers 2720/2720′ eachemit beams 2710/2710′, respectively, on the sides of the puddle to addheat to the puddle and aid in wetting the puddle so that the puddleshape is desirable. The lasers 2720/2720′ can be of the type describedherein and can be controlled as described above. That is, the lasers canbe controlled by the controller 195, or a similar device, to provide thedesired weld bead shape. Furthermore, rather than using two lasers toachieve the desired weld bead shape a single laser can be used with abeam splitter which splits the beam 2710 and directs the split beams tothe appropriate position on the weld puddle to achieve the desired weldbead shape. It is noted that the leading arc welding process is notdepicted in FIG. 27 for purposes of clarity.

In a further exemplary embodiment, a single laser beam 2710 can be usedthat is directed to the puddle just downstream of the arc process ordownstream of the hot wire 140 (in the travel direction) where the beam2710 is oscillated from side to side to aid in flattening the puddle. Insuch embodiments a single laser 2720 can be used and directed to areasof the puddle where it is desired to aid in wetting out the puddleduring welding. The control and operation of the laser 2720 is similarto the control and operation of the laser 120 described above inrelation to FIG. 1, etc.

FIG. 28 depicts another exemplary embodiment of the present invention.In this exemplary embodiment, a GTAW (or GMAW, FCAW, MCAW) electrode2801 is utilized for the arc welding process and a magnetic probe 2803is positioned adjacent to the electrode 2801 to control the movement ofthe arc during welding. The probe 2803 receives a current from themagnetic control and power supply 2805, which may or may not be coupledto the controller 195, and the current causes a magnetic field MF to begenerated by the probe 2803. The magnetic field interacts with themagnetic field generated by the arc and can thus be used to move the arcduring welding. That is, the arc can be moved from side to side duringwelding. This side to side movement is used to widen the puddle and aidin wetting out the puddle to achieve the desired weld bead shape.Although not shown for clarity, following the arc is a hot-wireconsumable as discussed herein to provide additional filling for theweld bead. The use and implementation of a magnetic steering system isgenerally known by those in the welding industry and need not bedescribed in detail herein.

It is, of course, understood that the embodiments in either of FIGS. 26and 28 (as well as the other shown embodiments described herein) can usethe laser 2720 to aid in the shape of the weld puddle as describedherein.

As indicated previously, exemplary embodiments of the present inventioncan be used in many different welding and joining operations. Thosejoining operations can include many different types of weldingapplications, including pipe welding. In fact, embodiments of thepresent invention can be used in pipe welding applications in which thepipe workpieces may have internal surfaces clad with a corrosionresistant material such as a nickel alloy. When such pipes are thenwelded together (end-to-end) the weld in the clad material must be heldto the same chemistry (for the corrosion protection) as the rest of theclad material. Therefore, the first pass in the clad or the “root pass”is important and must be made around the entire circumference of a pipejoint and have little or no porosity as described herein, includinglittle or no porosity at the beginning/end point of the weld joint. Thisis described in more detail below.

It is generally known that due to the amount of “sour” oil and gasfields which are corrosive in nature, the use of corrosion resistantclad piping is required to allow for extended life of the pipelinesections. In many cases the clad layer on the piping is a nickel basedclad material (“Ni clad layer”), having an appreciable thickness—e.g.,about 0.125 inch. Further, because the Ni clad layer is on the interiorsurface of the pipe, the Ni clad layers of two adjoining pipe sectionsare joined with a root pass—because the pipe sections are welded fromthe outside. This Ni clad layer presents a difficult root pass forconventional welding operations, because of the depth of the joint andbecause of the existence of the clad layer—which is to remain intact.These difficulties are especially present at the end point of the weld,where the welding interacts with the beginning of the weld. To achievethe desired strength and joint geometry and admixture at the end of thepipe weld it is necessary to have complete penetration. However, thispenetration with conventional welding operations can be difficult andresult in defects in the weld, such as porosity and incomplete fusion.Typically, these defects are only detected after the completion of theweld and cause significant cost and delay to repair.

As explained previously, embodiments of the present invention cansignificantly reduce or eliminate porosity, and can be used in deep andnarrow joints, to produce high quality welds at higher speeds thanpresently used or achieved. Reference is made to FIGS. 29 and 30, whereFIG. 29 is similar to FIG. 7B discussed previously. However, as shown aclad layer CL is located on a side of the workpiece 115 as shown. Theclad layer CL has a thickness CLt. The clad layer thickness CLt can varydepending on the application used. In some application, the clad layerthickness CLt can be in the range of 0.060 to 0.375 inches. When joiningthe workpieces 115 as shown, the clad layer CL is the area of theworkpiece which is joined via the root pass weld RP, which has a rootpass thickness RPt. In exemplary embodiments of the present invention,the nominal root pass thickness RPt (which is the thickness of the“land” and the deposited material) is in the range of 100 to 200% of thethickness of the clad layer thickness CLt. The thickness of the rootpass (RPt) will be such that the dilution of the base material into theroot pass will result in an acceptable chemistry in the depositedmaterial. While controlling the chemistry of the deposited material, thethickness RPt is such that it ensures that the adjacent clad layers CLare sufficiently joined. In exemplary embodiments of the presentinvention, the consumable 140 is of a material that can properly jointhe respective clad layers CL and provide the desired joint chemistryand strength. In exemplary embodiments of the present invention, theremainder of the joint is filled with the same consumable, while inother exemplary embodiments a consumable with a different chemistry canbe used for the remainder of the joint.

FIGS. 31 and 32 depict an exemplary pipe weld, using various embodimentsof the present invention. As shown, the root pas weld begins at a startpoint and proceeds around the pipe joint as described herein using alaser 120, beam 110 and consumable 140. FIG. 32 depicts a cross-sectionof the joint, showing the root pass RP, and the process as it nearscompletion of the weld when the operation returns to the start point SP.For purposes of clarity, the start point SP is the geometric centerpoint of the beam 110 on the root of the joint at the beginning of thejoining process. It should be noted that in exemplary embodiments of thepresent invention, the beam is angled such that it is perpendicular tothe tangent of the pipe circumference at the point of beam impact.However, in other exemplary embodiments, the beam 110 can be angled tobe +/−30 degrees relative to the normal. Further, although the figuresdepict the wire 140 to be in a “drag” mode (leading), in other exemplaryembodiments, the wire 140 can trial the beam 110, i.e. “pushing.” As theprocess returns to the start point, the puddle P makes contact with theroot pass RP at the start point SP. This contact and interaction betweenthe advancing puddle and the existing root pass weld at the start pointis the location of numerous defects in traditional welding processes,namely significant porosity. However, embodiments of the presentinvention are able to complete the root pass weld without these defects,e.g., porosity. Specifically, as the molten puddle P reaches, or getsnear, the start point SP, the process is controlled to minimizedisturbance of the existing root pass weld RP. Specifically, when thepuddle P reaches the start point the controller 195 causes the wirefeeder 150 to stop feeding the wire 140 into the weld. In otherexemplary embodiments, the wire feed speed is reduced, rather thanstopped. Additionally, in some embodiments, the controller 195 causesthe power supply 170 to stop heating the wire 140, or in otherembodiments, ramp down the heating current provided to the wire 140.Additionally, the controller 195 controls the laser power supply 130 toreduce the laser beam 110 energy density and/or decrease the laser beam110 interaction time at the joint. The beam 110 interaction time can bereduced by increasing the travel speed of the beam 110. By reducing theenergy density and/or reducing the interaction time of the beam, thekeyhole created by laser beam 110 is brought up to surface of thepuddle, resulting in less overall penetration into the existing rootpass RP weld joint. It is noted that the energy density of the beam 110can also be reduced by changing the focal length of the beam 110. Thisallows the weld to be tapered out of the root pass RP at the startpoint, and results in a shallower puddle. By combining the change inwire feeding rate (which can be reduced to zero) and reducing the energyfrom the beam 110 into the puddle, embodiments of the present inventionallow the end of the root pass RP to ramp out smoothly and withoutdefects, such as porosity. By controlling the process as describedabove, the root pass thickness RPt at or near the start point is withinthe range of 100 to 130% of the nominal root pass thickness RPt for theremainder of the root pass. That is, the process is controlled such thatthere is not an excessive “hump” of material at the end of the weldprocess, which can interfere with any subsequent weld passes. In someexemplary embodiments of the present invention, the root pass thicknessRPt within a range of +/−5° of the start point (relative to the center Cof the workpiece 115) is in the range of 100 to 130% of the nominal rootpass thickness RPt for the remainder of the weld.

The start of the ramp out process will depend on the configuration ofthe workpiece 115 (diameter of the pipe, the land thickness), weldingparameters being used (travel speed, laser spot size, wire feed, etc.)and the starting ramp procedures, e.g., how fast the welding ramps upand the ending ramp procedures, e.g., how fast the ramp out processramps down. In exemplary embodiments of the present invention, thecontroller 195 controls the process such that the ramp out process(describe above) begins when the geometric center of the beam 110 is ina range of 10 degrees before the start point SP to 5 degrees after thestart point SP (as measured relative to the center C of the workpiece115). In other exemplary embodiments, the ramp out process begins whenthe center of the beam is within a range of 2 degrees to 5 degreesbefore the start point SP. In other exemplary embodiments, the ramp outprocess begins when the center of the beam is within the range of +/−0.5to 5° (i.e., +/−0.5 degrees to +/−5 degrees) (as measured relative tothe center C of the workpiece 115) of the start point SP. In otherexemplary embodiments, the ramp out process begins when the center ofthe beam is within +/−0.5 to 2°. In other exemplary embodiments, theramp out process begins when the geometric center of the beam 110 at theroot is at the start point SP. In any event, the ramp out process shouldbe controlled such that end of the root pass joins smoothly with thebeginning of the root pass RP to provide a desirable weld joint. Inexemplary embodiments of the present invention, the energy density ofthe beam 110 is reduced to be within the range of 25 to 75% of theenergy density of the beam 110 during the overall welding of the rootpass RP. That is, the root pass RP is welded at a first energy densitylevel of the beam 110 and the ramp out is performed at a second energydensity, which is less than the first and at a level which is in therange of 50 to 75% of the first level. This can be accomplished inembodiments where the travel speed remains constant, or changes toachieve the desired exit profile. In other exemplary embodiments, theenergy density of the beam 110 can be ramped down from the first levelat a rate which smoothly reduces the depth of penetration by the beam110 and provides a desirable exit profile. In other exemplaryembodiments the energy density can be reduced in steps.

In exemplary embodiments of the present invention, the controller 195controls the process such that the ramp out at the end of the root passRP is completed within the range of 0.0 to 30° (angle A) past the startpoint SP. In other exemplary embodiments, the angle A is in the range of5 to 15° past the start point SP.

FIG. 33 depicts an illustration of an exemplary weld joint cross-sectionperformed in accordance with the embodiments discussed above, where theweld is completed. As can be seen, the “land” of the root jointtypically has a thickness less than the thickness of the clad layer CLt.This is typically done to maintain the desired composition of the rootpass, so as to not compromise the corrosive resistance properties of theclad layer. As is generally understood, the “land” is the thickness ofthe root joint portion of the workpiece 115 that butts up against anadjacent workpiece prior to joining. As shown, the weld begins at thestart point SP, where the laser beam 110 starts a puddle and then theconsumable 140 is dipped into the puddle to start the joining process.However, because the beginning of the weld involves a ramp up to thenormal welding parameters and speed, a region Z can be created where theworkpieces 115 are not completely welded at the start point SP. Then, asdescribed above, as the weld process comes around to the start point SP,and as it reaches or nears the start point SP, the wire feed speed isreduced (or stopped) so as to not deposit excessive amounts of materialinto the joint at the start point SP. As stated above, in exemplaryembodiments of the present invention, the thickness of the root pass ator near the start point (shown in FIG. 33 as the finish thickness Ft) isin the range of 100 to 130% of the nominal root pass thickness RPt forthe remainder of the weld. However, the power of the laser 110 should besuch that it can sufficiently penetrate into the weld at the start pointSP so as to reach any region Z which may not be fully welded at thestart. This ensures a complete weld at the start point region, while atthe same time preventing the deposition of excessive material. Thus, inexemplary embodiments, the laser power is reduced after the wire feedingspeed is slowed or stopped. The control of the wire feed speed and thelaser power is to be such that the joint is completely welded along itsentire periphery, including at the start point, and that the weld jointprofile at the interaction between the start point SP and the ending ofthe root pass has the desired chemistry, strength and geometry, suchthat there will be no physical interference with any subsequent fillpasses. Embodiments of the present invention can easily accomplish thisat high rates of speed and with little or no porosity, as describedpreviously.

Further, it should be noted that the above discussion was generallydirected to embodiments where a single laser and hot-wire assembly wasused to weld the entire circumference of a pipe. However, otherexemplary embodiments are not limited in this regard. That is,embodiments of the present invention can be used where multipleassemblies are used to weld a pipe at the same time, where each weldinghead unit is positionally radially from another. In such embodiments, aweld bead would be started by a first weld head (e.g., creating a startpoint) and a second, trailing weld head would come around and completethe weld pass. Embodiments of the present invention, can be used in suchconfigurations in that the trailing weld head would perform the rootpass ramp out as explained above.

Thus, embodiments of the present invention can weld high strength, cladworkpieces (such as pipes) with significant reductions in defects, andat significantly higher speeds, relative to conventional arc weldingtechniques. That is, embodiments of the present invention, can provideroot pass clad pipe/workpiece welds (as well as non-root pass welds) atthe speeds and porosity levels described previously herein, while at thesame time providing structurally sound and acceptable weld joints. Ofcourse, as with all exemplary embodiments of the present invention,either the workpiece or the welding head/devices, or both, can be movedrelative to each other to effect the welding operation.

While the invention has been described with reference to certainembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted withoutdeparting from the scope of the invention. In addition, manymodifications may be made to adapt a particular situation or material tothe teachings of the invention without departing from its scope.Therefore, it is intended that the invention not be limited to theparticular embodiments disclosed, but that the invention will includeall embodiments falling within the scope of the present application.

What is claimed is:
 1. A welding system, comprising: at least one highintensity energy source to create a weld puddle during a root pass on anarrow joint of a workpiece with a clad layer; a wire feeder thatadvances a filler wire to the weld puddle; a filler wire power sourcethat provides a filler wire heating signal to heat the filler wire whenthe filler wire is in contact with the weld puddle; and a controller tocontrol a weld ramp out process as the molten puddle advances to a startof an existing root pass weld, wherein the controller is configured to:control the at least one high intensity energy source to decrease anenergy output of the at least one high intensity energy source, reducean interaction time between the at least one high intensity energysource and the weld puddle, or both decrease the energy output of the atleast one high intensity energy source and reduce the interaction timebetween the at least one high intensity energy source and the weldpuddle, control the wire feeder to reduce wire feed speed or stop theadvancement of the filler wire, and control the filler wire power sourceto reduce a power level of the filler wire heating signal or stop thefiller wire heating signal to the filler wire, wherein the weld ramp outprocess is controlled such that, after completion of the root pass, athickness of a root pass weld in a region that is at or near the startpoint of the existing root pass weld is in a range of 100 percent to 130percent of a nominal root pass thickness of a remainder of the root passweld.
 2. The welding system of claim 1, wherein the workpiece is a pipeand the narrow joint is disposed circumferentially around the pipe, andwherein the clad layer is disposed on an inner surface of the pipe. 3.The welding system of claim 2, wherein a thickness of the clad layer isin a range of 0.60 inches to 0.375 inches, and wherein the nominal rootpass thickness is in a range of 100 percent to 200 percent of thethickness of the clad layer.
 4. The welding system of claim 2, whereinthe region is within a range of ±5 degrees of the start point relativeto a center of the pipe.
 5. The welding system of claim 1, wherein theat least one high intensity energy source includes a laser power sourcethat provides a laser beam to create the weld puddle.
 6. The weldingsystem of claim 5, wherein the controller begins the weld ramp outprocess when a geometric center of the laser beam is within a range of±0.5 to 5 degrees of the start point relative to a center of the pipe.7. The welding system of claim 6, wherein the control unit begins theweld ramp out process when the geometric center of the laser beam iswithin a range of ±0.5 to 2 degrees of the start point relative to acenter of the pipe.
 8. The welding system of claim 5, wherein the energyoutput of the laser source is decreased by reducing an energy density ofthe laser beam to be within 25 percent to 75 percent of an energydensity of the laser beam during the remainder of the root pass weld. 9.The welding system of claim 8, wherein the energy density of the laserbeam is reduced to be within 50 percent to 75 percent of the energydensity of the laser beam during the remainder of the root pass weld.10. The welding system of claim 5, wherein the interaction time betweenthe at least one high intensity energy source and the weld puddle isreduced by increasing a travel speed of the laser beam.
 11. The weldingsystem of claim 2, wherein the weld ramp out process stops within arange of 0.0 degrees to 30 degrees past the start point relative to acenter of the pipe.
 12. The welding system of claim 2, wherein the weldramp out process stops within a range of 5 degrees to 15 degrees pastthe start point relative to a center of the pipe.
 13. A welding method,comprising: creating a weld puddle using at least one high intensityenergy source; welding a root pass on a narrow joint of a workpiece witha clad layer; advancing a filler wire to the weld puddle; heating afiller wire when the filler wire is in contact with the weld puddle; andcontrolling a weld ramp out process such that, as the molten puddleadvances to a start of an existing root pass weld, the controllingincludes decreasing an energy output of the at least one high intensityenergy source, reducing an interaction time between the at least onehigh intensity energy source and the weld puddle, or both decreasing theenergy output of the at least one high intensity energy source andreducing the interaction time between the at least one high intensityenergy source and the weld puddle, reducing a wire feed speed of thefiller wire or stopping the advancement of the filler wire, and reducinga power level that heats the filler wire or stopping the heating of thefiller wire, wherein the weld ramp out process is controlled such that,after completion of the root pass, a thickness of a root pass weld in aregion that is at or near the start point of the existing root pass weldis in a range of 100 percent to 130 percent of a nominal root passthickness of a remainder of the root pass weld.
 14. The welding methodof claim 13, wherein the workpiece is a pipe and the narrow joint isdisposed circumferentially around the pipe, and wherein the clad layeris disposed on an inner surface of the pipe.
 15. The welding method ofclaim 14, wherein a thickness of the clad layer is in a range of 0.60inches to 0.375 inches, and wherein the nominal root pass thickness isin a range of 100 percent to 200 percent of the thickness of the cladlayer.
 16. The welding method of claim 14, wherein the region is withina range of ±5 degrees of the start point relative to a center of thepipe.
 17. The welding method of claim 13, wherein the at least one highintensity energy source includes a laser power source that provides alaser beam to create the weld puddle.
 18. The welding method of claim17, wherein the weld ramp out process begins when a geometric center ofthe laser beam is within a range of ±0.5 to 5 degrees of the start pointrelative to a center of the pipe.
 19. The welding method of claim 18,wherein the weld ramp out process begins when the geometric center ofthe laser beam is within a range of ±0.5 to 2 degrees of the start pointrelative to a center of the pipe.
 20. The welding method of claim 17,wherein the energy output of the laser source is decreased by reducingan energy density of the laser beam to be within 25 percent to 75percent of an energy density of the laser beam during the remainder ofthe root pass weld.
 21. The welding method of claim 20, wherein theenergy density of the laser beam is reduced to be within 50 percent to75 percent of the energy density of the laser beam during the remainderof the root pass weld.
 22. The welding method of claim 5, wherein theinteraction time between the at least one high intensity energy sourceand the weld puddle is reduced by increasing a travel speed of the laserbeam.
 23. The welding method of claim 14, wherein the weld ramp outprocess stops within a range of 0.0 degrees to 30 degrees past the startpoint, relative to a center of the pipe.
 24. The welding system of claim14, wherein the weld ramp out process stops within a range of 5 degreesto 15 degrees past the start point, relative to a center of the pipe.